Genes encoding melanocertin-4 receptor and methods of use

ABSTRACT

Genes encoding melanocortin receptors have been identified, isolated, cloned and localized to their chromosomal positions. These genes have been used to transfect mammalian cells lacking endogenous melanocortin receptors to induce expression. Additionally, melanocortin receptor binding, secondary signalling, and tissue distribution has been characterized. The genes and their gene products may therefore be used to provide therapeutic vehicles for the treatment of processes involving the function of melanocortin receptors.

Work on this invention was supported in part by National Institutes of Health Grants RO1DIC34306 and RO1DK33500, and funds from the University of Michigan Gastrointestinal Peptide Research Center (National Institutes of Health Grant P300K34933). The Government has certain rights in this invention.

This is a division of U.S. patent application Ser. No. 08/200,711, filed Feb. 17, 1994, U.S. Pat. No. 5,622,860.

FIELD OF THE INVENTION

The present invention relates generally to melanocortin receptors and, more specifically, to novel genes encoding melanocortin receptors.

    ______________________________________                                         GENBANK ACCESSION INFORMATION                                                  GENE             ACCESSION NO.                                                 ______________________________________                                         Melanocortin-3 Receptor                                                                         L06155                                                        Melanocortin-4 Receptor                                                                         L08603                                                        Melanocortin-5 Receptor                                                                         L22527                                                        ______________________________________                                    

BACKGROUND OF THE INVENTION

Melanocortins, products of pro-opiomelanocortin (POMC) post-translational processing, are known to have a broad array of physiological actions. Nakanishi, S. et al., Nature 278:423-427 (1979). Aside from their well known effects on adrenal cortical functions (adrenocorticotropic hormone, ACTH) and on melanocytes (melanocyte stimulating hormone, MSH), melanocortins have been shown to affect behavior, learning, memory, control of the cardiovascular system, analgesia, thermoregulation, and the release of other neurohumoral agents including prolactin, luteinizing hormone, and biogenic amines. De Wied, D. et al., Methods Achiev. Exp. Pathol. 15:167-199 (1991); De Wied, D. et al., Physiol. Rev. 62:977-1059 (1982); Gruber, K. A. et al., Am. J. Physiol. 257:R681-R694 (1989); Murphy, M. T. et al., Science 210:1247-1249 (1980); Murphy, M. T. et al., Science 221:192-193 (1983); Ellerkmann, E. et al., Endocrinol. 130:133-138 (1992) and Versteeg, D. H. G. et al., Life Sci. 38:835-840 (1986). Peripherally, melanocortins have been identified to have immunomodulatory and neurotrophic properties, and to be involved in events surrounding parturition. Cannon, J. G. et al., J. Immunol. 137:2232-2236 (1986); Gispen, W. H., Trends Pharm. Sci. 11:221-222 (1992); Wilson, J. F., Clin. Endocrinol. 17:233-242 (1982); Clark, D. et al., Nature 273:163-164 (1978) and Silman, R. E. et al., Nature 260:716-718 (1976). Furthermore, melanocortins are present in a myriad of normal human tissues including the brain, adrenal, skin, testis, spleen, kidney, ovary, lung, thyroid, liver, colon, small intestine and pancreas. Tatro, J. B. et al., Endocrinol. 121:1900-1907 (1987); Mountjoy, K. G. et al., Science 257:1248-1251 (1992); Chhajlani, V. et al., FEBS Lett. 309:417-420 (1992); Gantz, I. et al. J. Biol. Chem. 268:8246-8250 (1993) and Gants, I. et al., J. Biol. Chem. 268:15174-15179 (1993).

Recent studies have described an unexpected diversity of subtypes of receptors for the melanocortin peptides and determined that they all belong to the superfamily of seven transmembrane G-protein linked cell surface receptors. Mountjoy, K. G. et al., Science 257:1248-1251 (1992); Chhajlani, V. et al., FEBS Lett. 3:417-420 (1992); Gantz, I., J. Biol. Chem. 268:8246-8250 (1993) and Gantz, I. et al., J. Biol. Chem. (in press 1993). Although no ligand binding experiments were described, Mountjoy, K. G. et al., reported the gene sequences encoding the α-MSH receptor and the ACTH receptor. Science 257:1248-1251 (1992). Independently, Chhajlani, V. et al., reported a similar sequence for the α-MSH receptor and demonstrated specific binding of a stable MSH analogue to Cos-7 cells transfected with α-MSH receptor cDNA. FEBS Lett. 309:417-420 (1992). The α-MSH receptor has been identified as the melanocortin-1 receptor and the adrenocorticotropic hormone (ACTH) receptor as the melanocortin-2 receptor.

It would thus be desirable to isolate genes encoding melanocortin receptors. It would also be desirable to locate the chromosomal position of the melanocortin receptor genes. It would further be desirable to characterize melanocortin receptor binding and secondary signaling and determine tissue distribution of the melanocortin receptors. It would also be desirable to provide therapeutic vehicles for the treatment of processes involving the function of melanocortin receptors.

SUMMARY OF THE INVENTION

Five genes encoding the melanocortin-1, melanocortin-2, melanocortin-3, melanocortin-4 and melanocortin-5 receptors are set forth herein. The nucleic acid sequence of the gene encoding the human melanocortin-1 (MC1) receptor and its deduced 317 amino acid sequence are set forth in Sequence Listing ID Nos. 1 and 2, respectively. The nucleic acid sequence of the gene encoding human melanocortin-2 (MC2) receptor and its deduced 297 amino acid are set forth in Sequence Listing ID Nos. 3 and 4, respectively. The nucleic acid sequence of the gene encoding the human melanocortin-3 (MC3) receptor and its deduced 360 amino acid sequence, are set forth in Sequence Listing ID Nos. 5 and 6, respectively. The nucleic acid sequence of the gene encoding the human melanocortin-4 (MC4) receptor and its deduced 332 amino acid sequence, are set forth in Sequence Listing ID Nos. 7 and 8, respectively. The nucleic acid sequence of the gene encoding the mouse melanocortin-5 (mMC5) receptor and its deduced 326 amino acid sequence are set forth in Sequence Listing ID Nos. 9 and 10, respectively. The GenBank accession number for the MC3, MC4 and mMC5 receptor genes are LO6155, LO8603 and L22527, respectively.

The MC1 and MC2 receptor genes were previously described by Mountjoy, K. G., et al., in Science 257:1248-1251 (1992) and the MC1 receptor gene was also described by Chhajlani, V. et al., in FEBS Lett. 3:417-420 (1992). However, the nucleic and amino acid sequences set forth herein for the MC1 receptor differ from those previously described. More specifically, the sequences for the MC1 receptor herein differ from the sequences set forth in Chhajlani et al. in five nucleotide and two amino acid positions and differ from the sequences set forth in Mountjoy et al. in two nucleotide and two amino acid positions. The chromosomal localization of the MC1 and MC2 receptor genes is also disclosed herein. The MC1 receptor gene is localized to 16q24.3 and the MC2 receptor gene is localized to 18p11.2.

The receptors encoded by the MC3, MC4 and mMC5 receptor genes have also been characterized and the MC3 and MC4 receptor genes localized. More specifically, the MC3 receptor is activated primarily by the core heptapeptide sequence of the melanocortins with an adjacent carboxyl terminal tyrosine (Tyr²) being required for full activation. It is expressed in brain, placenta and gut tissues and the MC3 receptor gene was localized to chromosome loci 20q13.2-q13.3. The MC4 receptor is activated by amino acids in the carboxyl and amino terminal portions of the peptide, in particular Tyr² and Pro¹², with the core heptapeptide sequence being of lesser importance. It is expressed primarily in brain and its expression is notably absent in the adrenal cortex, melanocytes and placenta. The MC4 receptor gene was localized to chromosome 18q21.3. It was also determined that an amino terminal tyrosine and carboxyl terminal proline are determinates in the activation of the mouse mMC5 receptor, whereas the melanocortin core heptapeptide sequence is devoid of pharmological activity. The mMC5 receptor is expressed in lung, spleen and skeletal muscle. As discussed in detail below, the gene sequences, tissue distribution, and the profiles of the responses of the MC3, MC4 and mMC5 receptors to different melanocortins distinguish them from other melanocortin receptors as well as from each other.

Intracellular signalling pathways are also described herein. More specifically, it has been shown that the MC3 receptor is coupled to both cAMP and inositol phospholipid/Ca⁺⁺ mediated post-receptor signaling systems. A chimeric receptor cH2R/hMC3R-3i constructed for these studies is also provided herein. The present invention further provides the means to obtain an isolated protein which is a melanocortin receptor. The invention also provides the means to obtain antibodies directed at the melanocortin receptors described herein. Furthermore, the invention provides a method for detecting the presence of melanocortin receptors on cell surfaces. Likewise, the invention also provides a method for determining whether a ligand which is not known to be capable of binding to the melanocortin receptors described herein can bind to the respective receptor. The invention further provides a method of screening drugs to identify drugs which specifically interact with and bind to or effect the secondary signaling of melanocortin receptors.

It will be appreciated that therapeutic interventions addressing both normal physiological and pathophysiological processes which utilize the melanocortin receptors, the Genes encoding these receptors and the distribution and characterization information set forth herein, are also contemplated.

Additional objects, advantages, and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The various advantages of the present invention will become apparent to one skilled in the art by reading the following specification and subjoined claims and by referencing the following drawings in which:

FIGS. 1A and 1B are Northern blots showing tissue distribution of the MC4 receptor;

FIGS. 2A and 2B are graphs showing the generation of cAMP in L-cells transfected with the MC1 and MC3 receptor genes, respectively, in response to various melanocortins;

FIGS. 3A and 3B are graphs showing the generation of cAMP in L-cells transfected with the MC1 and MC3 receptor genes, respectively, in response to various truncated ACTH peptides;

FIG. 4 is a graph showing the generation of cAMP in response to ACTH and α-MSH in wild type COS-1 cells and COS-1 cells transiently transfected with the MC4 receptor gene;

FIG. 5 is a graph showing the generation of cAMP in L-cells transfected with the MC4 receptor gene in response to various whole and truncated melanocortins;

FIG. 6 shows the core heptapeptide amino acids of various melanocortins Sequence Listing ID NO13-23;

FIGS. 7A and 7B are graphs showing the measurement of intracellular cAMP content after stimulation of the MC3 receptor and the MC4 receptor, respectively, with natural melanocortins and synthetic peptides in Hepa cells;

FIGS. 8A and 8B are graphs showing the measurement of intracellular cAMP content after stimulation of the MC3 receptor and the MC4 receptor, respectively, with truncated melanocortin peptides in Hepa cells;

FIGS. 9A and 9B are graphs showing a comparison of the contribution of an acetylated N-terminal serine on the generation of intracellular cAMP at the MC3 receptor and MC4 receptor, respectively;

FIG. 10 is a graph showing the generation of cAMP in L-cells transfected with the mMC5 receptor in response to various melanocortins;

FIG. 11 is a graph showing the generation of cAMP in L-cells transfected with the mMC5 receptor in response to various truncated peptides;

FIG. 12 is a graph showing the inhibition by α-MSH, ACTH (1-13) and ACTH (1-39) of ²⁵¹ I! NDP-MSH binding to L-cells transfected with the mMC5 receptor;

FIGS. 13A and 13B are graphs showing an increase in intracellular cAMP content and total ³ H! IP production, respectively, in Hepa cells transfected with the MC3 receptor;

FIG. 14 is a graph showing time dependent generation of ³ H! IP3 in Hepa cells in response to varying doses of α-MSH;

FIG. 15 is a bar graph showing the effect of forskolin and dibutryl cAMP on α-MSH stimulated ³ H! IP production in transfected Hepa cells;

FIGS. 16A and 16B are graphs showing the effect of pretreatment of transfected Hepa cells with the protein kinase A inhibitor H-89 or its inactive analogue H-85 on α-MSH stimulated total ³ H! inositol phosphate (IP) production;

FIGS. 17A, 17B and 17C are a set of graphs showing the effect of α-MSH, vasopressin and EDTA, respectively, on Ca⁺⁺ !i of transfected Hepa cells in the presence or absence of H-89 pretreatment; and

FIGS. 18A, 18B, 18C and 18D are a set of graphs showing dose-response curves for histamine stimulated changes in cAMP content and ³ H! IP production in Hepa cells wherein FIGS. 18A and 18C depict cells transfected with wild type cH2R and FIGS. 18B and 18D depict cells transfected with the chimeric cH2R/hMC3R-3i.

DESCRIPTION OF SEQUENCE LISTINGS

Sequence Listing ID No. 1 is the nucleotide sequence of DNA encoding the melanocortin-1 receptor.

Sequence Listing ID No. 2 is the deduced amino acid sequence of the melanocortin-1 receptor.

Sequence Listing ID No. 3 is the nucleotide sequence of DNA encoding the melanocortin-2 receptor.

Sequence Listing ID No. 4 is the deduced amino acid sequence of the melanocortin-2 receptor.

Sequence Listing ID No. 5 is the nucleotide sequence of DNA encoding the melanocortin-3 receptor.

Sequence Listing ID No. 6 is the deduced amino acid sequence of the melanocortin-3 receptor.

Sequence Listing ID No. 7 is the nucleotide sequence of DNA encoding the melanocortin-4 receptor.

Sequence Listing ID No. 8 is the deduced amino acid sequence of the melanocortin-4 receptor.

Sequence Listing ID No. 9 is the nucleotide sequence of DNA encoding the melanocortin-5 receptor.

Sequence Listing ID No. 10 is the deduced amino acid sequence of the melanocortin-5 receptor.

Sequence Listing ID No. 11 is the nucleotide sequence of an oligonucleotide used as a 5' PCR primer.

Sequence Listing ID No. 12 is the nucleotide sequence of an oligonucleotide used as a 3' PCR Primer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Five sequences encoding the human melanocortin-1 (MC1), melanocortin-2 (MC2), melanocortin-3 (MC3), melanocortin-4 (MC4) and mouse melanocortin-5 (mMC5) receptors have been cloned and sequenced. Their nucleic acid and corresponding amino acid sequences are set forth in Sequence Listing ID Nos. 1-10. The MC1 and MC2 receptor genes have been localized to chromosome 16q24.3 and 18p11.2, respectively. The MC3 receptor gene was localized to chromosome loci 20q13.2-q13.3. The MC4 receptor gene was localized to chromosome 18q21.3.

The MC3 receptor is primarily activated by the heptopeptide core of melanocortins. It is expressed in brain, placenta and gut tissues. The MC4 receptor is activated by amino acids in the carboxyl and amino terminal portions of the peptide. It is expressed primarily in brain and its expression is notably absent in the adrenal cortex, melanocytes and placenta. The mMC5 receptor is also activated by amino acids in the carboxyl and amino terminal portions of the peptide and is expressed in lung, spleen and skeletal muscle. As discussed in detail below, the gene sequences, tissue distribution and the profiles of the responses of the MC3, MC4 and MC5 receptors to different melanocortins distinguish them from other melanocortin receptors as well as from each other.

The MC1 and MC2 receptor genes have been previously described in Mountjoy, K. G., et al., in Science 257:1248-1251 (1992) and the MC1 receptor gene was also described by Chhajlani, V. et al., in FEBS Lett. 3:417-420 (1992). The nucleic and amino acid sequences for the MC1 receptor set forth herein differ from the sequences set forth in Mountjoy et al. in two nucleotide and two amino acid positions. Likewise, the MC1 receptor sequences of the present invention differ from the sequences set forth in Chhajlani et al. in five nucleotide and three amino acid positions.

It will be appreciated that the nucleic and amino acid sequences of the present invention can include some variation from the sequences represented by and complementary to the sequences set forth in the Sequence Listing but must be substantially represented by or complementary to those set forth therein. By "substantially represented by" or "substantially complementary to" is meant that any variation therein does not impair the functionality of the sequence to any significant degree. As used herein, the term "nucleic acid" is intended to mean natural and synthetic linear and sequential arrays of nucleotides and nucleosides, e.g. in cDNA, genomic DNA (gDNA), mRNA, and RNA, oligonucleotides, oligonucleosides and derivatives thereof. It will also be appreciated that such nucleic acids can be incorporated into other nucleic acid chains referred to as "vectors" by recombinant-DNA techniques such as cleavage and ligation procedures. The terms "fragment" and "segment" are as used herein with reference to nucleic acids (e.g., cDNA, genomic DNA, i.e., gDNA) are used interchangeably to mean a portion of the subject nucleic acid such as constructed artificially (e.g. through chemical synthesis) or by cleaving a natural product into a multiplicity of pieces (e.g. with a nuclease or endonuclease to obtain restriction fragments). As used herein, "A" represents adenine; "T" represents thymine; "G" represents guanine; and "C" represents cytosine; except where otherwise indicated.

As referred to herein, the term "encoding" is intended to mean that the subject nucleic acid may be transcribed and translated into the subject protein in a cell, e.g. when the subject nucleic acid is linked to appropriate control sequences such as promoter and enhancer elements in a suitable vector (e.g. an expression vector) and when the vector is introduced into a cell. The term "polypeptide" is used to mean three or more amino acids linked in a serial array.

The term "capable of hybridizing under stringent conditions" is used to mean annealing a first nucleic acid to a second nucleic acid under stringent conditions (defined below). For example, the first nucleic acid may be a test sample, and the second nucleic acid may be the sense or antisense strand of a melanocortin receptor gene of the present invention. Hybridization of the first and second nucleic acids is conducted under stringent conditions, e.g. high temperature and/or low salt content, which tend to disfavor hybridization in 6×SSC, at 42° C. in aqueous solution followed by washing with 1×SSC, at 55° C. in aqueous solution. (Other experimental conditions for controlling stringency are described in Maniatis, T. et al., Molecular Cloning; A Laboratory Manual, Cold Springs Harbor Laboratory, Cold Springs, N.Y., 1982 at pages 387-389 and also Sambrook, Fritsch, and Maniatis, Molecular Cloning; A Laboratory Manual, Second Edition, Volume 2, Cold Springs Harbor Laboratory, Cold Springs, N.Y., 1989, pages 8.46-8.47, both of which are herein incorporated by reference).

The Specific Examples set forth below further describe the present invention. In particular, Specific Example I describes the isolation and cloning of the melanocortin receptors. For the initial gene isolation experiments, total RNA obtained from HeLa cells and U937 cells via the acid guanidiniym thiocyanatephenol-chloroform method were reverse transcribed using avian myeloblastoma virus reverse transcriptase. Chomczynski, P. et al., Anal. Biochem. 162:1900-1907 (1987). The cDNAs thus obtained functioned as templates for the polymerase chain reaction (PCR) primed with oligonucleotides based on homologous regions of the third and sixth transmembrane domains of G-protein linked receptors as previously described. Libert, R. et al., Science 244:569-572 (1989). The DNA obtained by PCR was cut with an appropriate restriction enzyme corresponding to the linker portion of the oligonucleotide and then electrophoresed. DNA bands were excised from the gel and subcloned directly into the M13 sequencing vector. Dideoxynucleotide sequencing was then performed. Initial PCR experiments resulted in the isolation of DNA fragments encoding two novel G-protein linked receptors. These receptors were subsequently identified as the melanocortin-1 (MC1) and melanocortin-3 (MC3) receptors. Oligonucleotides based on highly conserved sequences in the second intracytoplasmic loop and the seventh transmembrane domain of these two receptors were subsequently constructed to search for other members of this receptor gene family. Using both human and murine genomic DNA as substrate for further PCR reactions, three additional gene fragments encoding members of this novel receptor family were isolated using these latter primers. These DNA fragments were subsequently used to isolate the melanocortin-2 (MC2), melanocortin-4 (MC4), and melanocortin-5 (MC5) receptors.

In Specific Example II, expression confirming the identification of the melanocortin receptors is described. For these experiments, the coding regions of the receptors were subcloned into the eukaryotic expression vector CMVneo using the PCR according to methods previously described for receptor expression studies. Brown, N. A. et al., J. Biol. Chem. 265:13181-13189 (1990) and Gantz, I. et al., PNAS (USA) 88:429-433 (1991). Various cells lines were transfected using a calcium phosphate co-precipitation method or lipofection. Chen, C. A. et al., Biotechniques 6:632-638 (1988) and Felgner, P. L. et al., PNAS (USA) 84:7413-7414 (1987). The transiently or stably transfected cell lines served as the substrate for the detailed pharmacological studies and investigations of secondary messenger signal transduction.

In Specific Example II, the tissue distribution of the MC3, MC4 and mMC5 receptors is also described. For characterization of tissue distribution of these receptors, Northern blot analysis, PCR, and in situ hybridization were used. By Northern blot analysis and PCR/Southern it was found that the MC3 receptor is present in brain, placental, and gut tissues and by Northern blot analysis it was found that the MC4 receptor is limited to brain. In situ hybridization of rodent brain sections with probes specific for the MC3 and MC4 receptors revealed that these receptors are present in the cortex, thalamus, hypothalamus, and hippocampus of the brain. Also by Northern blot analysis, it was found that mMC5 receptor is present in mouse lung, spleen and skeletal muscle.

In Specific Example III, pharmacological experiments examining the structure and activity of the receptors are described. It was found that the MC3 receptor is capable of recognizing the core heptapeptide sequence shared by all the melanocortin peptides (Met-Glu-His-Phe-Arg-Tyr-Gly); Sequence Listing ID NO. 17, and hence responds to all melanocortins with equal potency and efficacy. It was also found that adjacent amino acids of the melanocortin peptides are of primary importance. Experiments were also performed on the MC3 and MC4 receptors with synthetic melanocortin peptides containing specific amino acid substitutions which confirmed the above pharmacological results. The MC3 receptor is activated primarily by the core heptapeptide sequence of melanocortins with an adjacent carboxyl terminal tyrosine (Tyr²) being required for full activation. The MC4 receptor is activated by amino acids in the carboxyl and amino terminal portions of the peptide (especially Tyr² and Pro¹²) with the core heptapeptide sequence being of lesser import. It was also determined that an amino terminal tyrosine and carboxyl terminal proline are determinates in the activation of the mMC5 receptor whereas the melanocortin core heptapeptide sequence is devoid of pharmalogical activity. The physiological studies of the cloned receptors have uncovered unique aspects regarding the regulation of the pathways of signal transduction used by these receptors. It will thus be appreciated to those skilled in the art that subtype specific drugs are also contemplated by the present invention.

In Specific Example IV, experiments demonstrating the intracellular signalling mechanisms activated by melanocortin receptors are described. A chimeric receptor cH2R/hMC3R-3, constructed for these studies is also described herein. These experiments indicate that the MC3 receptor is coupled to both cAMP and inositol phospholipid/Ca⁺⁺ mediated post-receptor signalling systems. Such information is useful to determine normal, abnormal and altered functioning of the receptor.

In Specific Example V, chromosomal localization of the human melanocortin receptor genes is described. It was found that the MC1 receptor gene is localized to 16q24.3, the MC2 receptor gene is localized to 18p.11.2, the MC3 receptor gene is localized to 20q13.2-q13.3 and the MC4 receptor gene is localized to 18q21.3. This information provides the ability to determine abnormalities such as translocations in the genes which encode the receptors by using well known hybridization techniques.

It will be appreciated that the genes of the present invention encode for proteins which, by using methods well known in the art, can be isolated. Examples of such proteins are those having substantially the same amino acid sequences as the amino acid sequences set forth in the Sequence Listing. A method for obtaining an isolated melanocortin receptor is by expressing DNA encoding the receptor in a suitable host, such as a bacterial, yeast, or mammalian cell, and recovering the melanocortin receptor after it has been expressed in such a host.

This invention also provides an antibody directed to a melanocortin receptor of the present invention. Such an antibody may be serum-derived or monoclonal and may be prepared using methods well known in the art. For example, cells may be used as immunogens to raise such an antibody. Alternatively, synthetic peptides may be prepared using commercially available machines and the amino acid sequences shown in the Sequence Listing. As a still further alternative, DNA, such as a cDNA or a fragment thereof, may be cloned and expressed and the resulting polypeptide recovered and used as an immunogen. One example of such an antibody is a monoclonal antibody directed to an epitope of the melanocortin receptor present on the surface of a cell and having an amino acid sequence substantially the same as any part of one amino acid sequence set forth in the Sequence Listing.

Still further, this invention provides a method of detecting the presence of a melanocortin receptor on the surface of a cell. This method comprises contacting the cell with a monoclonal or serum-based antibody directed to an exposed epitope on the melanocortin receptor under conditions permitting binding of the antibody to the melanocortin receptor, and detecting the presence of the antibody bound to the cell, and thereby the presence of the melanocortin receptor on the surface of the cell. Such a method is useful in determining whether a given cell is defective relative to the expression of melanocortin receptors on the surface of the cell.

It will also be appreciated that the present invention provides vectors capable or adapted for expression in a bacterial, yeast, or mammalian cell which comprise DNA encoding one of the melanocortin receptors of the present invention or DNA or cDNA having a coding sequence substantially the same as any one of the coding sequences set forth in the Sequence Listing and the regulatory elements necessary to express such DNA in the bacterial, yeast, or mammalian cell. With respect to the latter, those skilled in the art will readily appreciate that numerous vectors may be constructed utilizing existing plasmids, viruses, bactedophages and the like and adapted as appropriate by methods known to those skilled in the art to contain regulatory elements necessary to express the DNA in the mammalian cell. Numerous mammalian cells may be used including, for example, the mouse fibroblast cell NIH3T3, L-cells, CHO cells, HeLa cells, Hepa cells and COS-1 cells. DNA encoding a melanocortin receptor may be otherwise introduced into mammalian cells, e.g. by calcium phosphate coprecipitation, to obtain mammalian cells which comprise DNA, e.g., cDNA or a vector encoding the receptor.

It will further be appreciated that the invention also provides a method of detecting the presence of mRNA coding for the melanocortin receptors of the present invention in a cell. This method comprises obtaining total mRNA from the cell by using methods well known in the art, and contacting the mRNA so obtained with cDNA having a coding sequence substantially the same as one of the coding sequences of the genes of the present invention under hybridizing conditions, detecting the presence of mRNA hybridized to the cDNA, and thereby detecting the presence of mRNA coding for the melanocortin receptor in the cell.

This invention additionally provides a DNA probe useful for detecting, in a sample, a nucleic acid encoding the melanocortin receptor. Such a probe comprises a nucleic acid molecule of at least about 17-21 nucleotides having a sequence complementary to a sequence included within the nucleic acid sequences set forth in the Sequence Listing. Such nucleic acid probe technology is well known to those skilled in the art who will readily appreciate that such probes may vary greatly in length and may comprise a detectable label, such as a radioisotope or fluorescent dye, to facilitate detection of the probe.

The present invention also provides a method for determining whether a ligand, such as a known or putative drug, which is not known to be capable of binding to melanocortin receptors of the present invention, can bind to the receptors. This method comprises contacting a mammalian cell with the ligand under conditions permitting binding of ligands previously known to bind to the melanocortin receptors and detecting the presence of any of the ligand bound to the receptors. An example of a mammalian cell is a mammalian cell comprising a vector which comprises a DNA molecule encoding a melanocortin receptor of the present invention, or DNA or cDNA molecules having coding sequences substantially the same as one of the coding sequences shown in the Sequence Listing. Also, the present invention provides a method of screening drugs to identify drugs which specifically interact with, and bind to, a melanocortin receptor on the surface of a cell. This method comprises contacting a mammalian cell which is expressing a melanocortin receptor with a plurality of drugs, known or putative, determining those drugs which bind to the mammalian cells, and thereby identifying those drugs which bind to the mammalian cell, and thereby identifying drugs which specifically interact with, and bind to, the melanocortin receptor.

The following Specific Examples further describe the present invention.

SPECIFIC EXAMPLE 1 ISOLATION Materials and Methods

Polymerase Chain Reaction (PCR).

Total RNA obtained from HeLa cells (a human cervical cancer cell line) and U937 cells (a human histiocytic lymphoma cell line) via the acid guanidinium thiocyanate-phenol-chloroform method of Chomczynski, P. et al., Anal. Biochem. 162:156-159 (1987) was reverse transcribed using avian myeloblastoma virus reverse transcriptase. The cDNAs thus obtained functioned as templates for polymerase chain reactions primed with oligonucleotides based on homologous regions of the third and sixth transmembrane domains of G protein-linked receptors as described by Libert, R. et al., Science 244:569-572 (1989) and Gantz, I. et al. PNAS (USA) 88:429-433 (1991). Initially two partial length DNA clones for G protein-linked receptors were isolated, and these were utilized to obtain full-length genomic clones by screening a genomic library as described below. Highly conserved sequences in the second intracytoplasmic loop and the seventh transmembrane domain of these receptors served as the basis for constructing oligonucleotides to be used to search for other members of this receptor gene family (5'PCR primer TACGCA/GCTG/CCGCTACCACAGCATC) (Sequence Listing ID No. 11) and 3' PCR primer GAAG/AGCA/GTAT/GATGAA/GG/TGGGTCA/GAT) (Sequence Listing ID No. 12). Oligonucleotides were synthesized by the Molecular Biology Core of the University of Michigan Gastrointestinal Peptide Research Center using an Applied Biosystems model 380B DNA synthesizer. The conditions for the PCR were as follows: denaturation for 1.5 min at 94° C., annealing for 2 min at 45° C., and extension for 4 rain at 72° C. The reaction was carded out for 30 cycles, and then 20% of the product was added to fresh buffer and enzyme and subjected to an additional 30 cycles. The final reaction products were phenol-extracted and ethanol-precipitated. The DNA was cut with an appropriate restriction enzyme corresponding to the linker portion of the oligonucleotide and then electrophoresed on a 1% NuSieve, 1% Seaplaque gel (FMC, Rockland, Me.). DNA bands were cut out of the gel and subcloned directly into the M13 sequencing vector. Dideoxynucleotide sequencing was then performed using Sequenase version 2 (United States Biochemical Corp.).

Genomic Cloning.

Partial length PCR-derived clones obtained as described above were random-primed with ³² P and used as probes to screen a human and a mouse EMBL3 phage library (Clontech, Palo Alto, Calif.). Under hybridization 6×SSC (0.9M NaCl, 90 mM sodium citrate, pH 7.0), 5×Denhardt's solution (0.1% Ficoll, 0.1% polyvinylpyrrolidone, 0.1% bovine serum albumin), 0.1M Hepes, pH 7.0 100 μg/ml salmon sperm, 10 mg/ml dextran sulfate at 55° C.! and wash conditions (successive washes with 6×SSC, 4×SSC, and 2×SSC at 50° C.) single clones were isolated. Phage DNA preparations were made by the plate lysate method as described in Taonis, P. A. et al., Bio/Techniques 6:950-951 (1988), and the inserts were restriction-mapped and examined by Southern blot analysis. Dideoxynucleotide sequencing of fragments containing the receptor coding regions subcloned into M13 was then performed.

Results

Melanocortin-1 Receptor.

The melanocortin-1 (MC1) receptor gene encodes for a protein 317 amino acids in length. The nucleotide and deduced amino acid sequences of the MC1 receptor are set forth in Sequence Listing ID Nos. 1 and 2, respectively. Receptors having the greatest degree of homology with the melanocortin receptor family are those of the adenosine and catecholamine receptor families. The nucleotide sequence obtained for MC1 receptor differed from that reported by Mountjoy, K. G. et al., in Science 257:1248-1251 (1992), in two nucleotide and two amino acid positions, and from that reported by Chhajlani, V. et al., in FEBS Lett. 309:417-420 (1992), in five nucleotide and three amino acid positions. Specifically, at nucleotide positions 485 and 488 of the MC1 receptor gene, Mountjoy et al. disclose guanine and adenine, respectively, rather than cytocine and guanine as disclosed herein. Mountjoy et al., therefore, disclose proline and arginine at amino acid positions 162 and 163, respectively, rather than arginine and glutamine as disclosed herein. At nucleotide positions 269, 270, 488, 490 and 491 Chhajlani et al. disclose guanine, cytosine, guanine, cytosine and guanine respectively, rather than cytosine, guanine, adenine, guanine and cytosine as described herein. Chhajlani et al., therefore, disclose serine, arginine and arginine at amino acid positions 90, 163 and 164, respectively, rather than threonine, glutamine and alanine as disclosed herein. Comparison of several amino acid sequences of melanocortin receptors are shown in Gantz I. et al., J. Biol. Chem. 268:8246-8250 (1993).

Melanocortin-2 Receptor.

The melanocortin-2 (MC2) receptor gene encodes for a protein 297 amino acids in length. The nucleotide and deduced amino acid sequence of MC2 receptor are set forth in Sequence Listing ID Nos. 3 and 4, respectively.

Melanocortin-3 Receptor.

The melanocortin-3 (MC3) receptor gene is an intronless gene encoding an apparent seven-transmembrane-spanning protein of 360 amino acids in length. Sequencing Listing ID Nos. 5 and 6 represent the nucleotide and deduced amino acid sequences, respectively, of the MC3 receptor gene. As shown in Gantz et al., J. Biol. Chem. 268:8246-8250 (1993), the MC3 receptor shares approximately 60% nucleotide sequence homology and 45% amino acid homology with the MC1 receptor and MC2 receptor.

Melanocortin-4 Receptor.

The melanocortin-4 (MC4) receptor gene is an intronless gene encoding a protein of 332 amino acids in length and with apparent seven transmembrane topography. As shown in Gantz, I., et al., J. Biol. Chem. 268:15174-15179 (1993), the MC4 receptor is structurally most similar to the MC3 receptor with which it shares 58% and 76% overall amino acid identity and similarity, respectively. Sequence Listing ID Nos. 7 and 8 represent the nucleotide and deduced amino acid sequences of the MC4 receptor, respectively.

Melanocortin-5 Receptor.

The mouse melanocortin-5 (mMC5) receptor gene encodes a protein of 325 amino acids in length. Sequence Listing ID Nos. 9 and 10 represent the nucleotide and deduced amino acid sequences of the mMC5 receptor, respectively. The highest overall homology of this receptor is to the human MC4 receptor with which it shares 63.7% amino acid identity and 77.6% amino acid similarity. Deduced amino acid sequences of rodent melanocortin receptors have been published only for the mouse melanocortin-1 receptor (mMC1 receptor or murine α-MSH receptor), Mountjoy, K. G., et al., Science 257:1248-1251 (1992), and the rat melanocortin-3 (rMC3) receptor, Roselli-Rehfuss, L., et al., PNAS 90:8856-8860 (1993). By comparison to their human melanocortin receptor counterparts, these mouse receptors share considerably greater sequence homology within a single receptor subtype than they do to each other.

SPECIFIC EXAMPLE 2 EXPRESSION and DISTRIBUTION Materials and Methods

Receptor Expression.

The coding regions of the receptors were subcloned into the eukaryotic expression vector CMVneo as described in Brown, N. A. et al., J. Biol. Chem. 265:13181-13189 (1990) using the PCR according to methods previously described in Gantz, I. et al., PNAS (USA) 88:429-433 (1991). The sequences were subsequently checked by nucleotide sequencing to insure that no sequence errors were induced by PCR. L-cells (a mouse fibroblast-like cell line) were transfected using a calcium phosphate co-precipitation method as described in Chen, C. A. et al. Bio/Techniques 6:632-638 (1988). Permanently transfected L-cells were selected by resistance to the neomysin analogue G418, and receptor mRNA expression was checked by Northern blot analysis. A rat hepatoma cell line (Hepa) which lacks endogenous melanocortin receptors was also transfected with the CMVneo/MC3R and CMVneo/MC4R constructs. COS-1 cells which were transiently transfected with the CMVneo/MC4R gene construct by lipofection as described in Felgner, P. L. et al., PNAS (USA) 84:7413-7417 using the Lipofectin Reagent (Life Technologies Inc.) were split into 12-well plates after 24 hr and assayed 36 hr post-transfection.

Northern Blotting.

Total RNA was extracted from cell lines and tissues using the acid guanidinium thiocyanate-phenol-chloroform method as described in Chomczynski, P. et al., Anal Biochem. 162:156-159 (1987). Poly(A)⁺ RNA was obtained using oligo(dT)-cellulose chromatography with the Poly(A) Quik mRNA isolation kit (Stratagene, La Jolla, Calif.). Alternatively some poly(A)⁺ was obtained directly from tissue using the Fast Track kit (Invitrogen, San Diego, Calif.). A commercially available human multiple tissue Northern blot (Clontech, Palo Alto, Calif.) was also used. RNA was transferred to nitrocellulose and hybridized in 50% formamide, 5×SSPE (0.75M NaCl, 0.05M NaH₂ PO₄, 0.005M Na₂ EDTA, pH 7.4), 10×Denhardt's solution, 100 μg/ml salmon sperm DNA, and 2% sodium dioctyl sulfate for 18 hr according to standard methods. Sambrook, J. et al., Molecular Cloning: A Laboratory Manual, 2nd Ed., Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y. (1989). Human and rat tissues were hybridized at 42° C. using a random-primed ³² P-labeled human or mouse probe, respectively. Canine tissue was hybridized with a rat probe at a lower temperature (40° C.) to compensate for cross-speices sequencing mismatch. Blots were exposed to XAR-5 film for 24-72 hr.

PCR/Southern Blotting.

RNA extracted by the acid guanidinium thiocyanate-phenol-chloroform method was treated with 50 units of RNase-free DNase I (Boehringer Mannheim) for 1 hr at 25° C., then reverse transcribed with avian myeloblastosis reverse transcriptase using oligo(dT)₁₂₋₁₈ as primer. Human stomach and duodenal mucosa cDNA thus generated was used as template for PCR using primer oligonucleotides specific for the 5'- and 3'- untranslated portions of the melanocortin receptor sequence. The primers used for the PCR reaction with rat pancreatic cDNA were the nonspecific second intracytoplasmic loop and seventh transmembrane oligonucleotides described above. Aside from the DNase treatment, the PCR reactions were controlled for possible genomic DNA contamination by conducting parallel reactions using RNA samples prior to reverse transcription as template. Similarly, PCR reactions were conducted with laboratory water as template to verify that there was no contamination of reagents from any source. Each PCR reaction was conducted over 30 or 60 cycles as described above. The products were electrophoresed on a 1% Nusieve, 1% Seaplaque gel, stained with ethidium bromide, and photographed under ultraviolet illumination. To verify that the bands obtained by PCR were generated from melanocortin receptor cDNA, they were transferred to nitrocellulose using standard Southern blotting techniques as described in Sambrook, J. et al., Molecular Cloning: A Laboratory Manual, 2nd Ed., Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y. (1989). The coding region of the gene labeled with ³² P by random priming was then used to probe the blots under stringent hybridization (65° C.) and wash conditions (final wash 0.1×SSC at 65° C.). Blots were exposed to XAR-5 film for 3-6 hr at -80° C.

In Situ Hybridization.

Adult male mice were sacrificed by cervical dislocation and their brains removed and frozen in liquid isopentane (-30° C.) for 30 seconds. Frozen tissue was sectioned on a Slee cryostat (15 μm), thaw-melted onto polylysine-coated slides, and stored at -80° C. For further investigations, slides were transferred directly to 4% buffered formaldehyde for 60 min at room temperature. Following 3 rinses in 2×SSC, the sections were treated with proteinase K (1 μg/ml in 100 mM Tris, pH 8.0, 50 mM EDTA) for 10 min at 37° C., then rinsed in water and treated with a mixture of 0.1M triethanolamine, pH 8.0, and acetic anhydride (400:1, v/v) with stirring for 10 min. The sections were again rinsed in water, dehydrated through graded alcohols, and air-dried. As a control, prior to treatment with proteinase K, some sections were incubated with RNase A (200 μg/ml in 100 mM Trix, pH 8.0 and 0.5M naCl) for 30 min at 37° C. All sections were hybridized with a ³⁶ S-UTP/³⁵ S-CTP-labeled riboprobe generated from a 461-base fragment of the melanocortin receptor clone. cRNA probes were diluted in hybridization buffer (75% formamide, 10% dextran sulfate, 3×SSC, 50 mM Na₂ PO4, pH 7.4, 1×Denhardt's, 0.1 mg/ml yeast tRNA, 10 mM dithiothrietol) to a final concentration of 2×10⁶ dpm/30 μl. After a 55° C. overnight hybridization, sections were rinsed in 2×SSC and treated with RNase A (200 μg/ml for 60 min at 37° C.). The slides were rinsed in 1×SSC, washed in 0.1×SSC at 68° C. for 90 min, rinsed in water, dehydrated in graded alcohols, and air-dried. Sections were then exposed to Kodak XAR-5 film for 10 days and developed.

Results

Melanocortin-3 Receptor.

Tissue distribution further differentiates the MC3 receptor from the previously described α-MSH (melanocortin-1) and ACTH (melanocortin-2) receptors. As reported in Mountjoy, K. G. et al., Science 257:1248-1251 (1992) the MC1 receptor was expressed in melanoma cells but not in other tissues, whereas the MC2 receptor was expressed only in the adrenal gland. In contrast, demonstrated by Northern blot hybridization, the MC3 receptor is expressed in brain and placenta but not expressed in either melanoma cells or in adrenal tissue. Gantz et al., J. Biol. Chem. 268:8246-8250 (1993). Additionally, in situ hybridization demonstrated that the MC3 receptor is expressed in the cortex, thalamus, hippocampus, and hypothalamus. Gantz et al. supra. Thus the MC3 receptor may partake in mediating some of the putative actions of melanocortin peptides in higher cortical functions such as behavior. The magnitude of melanocortin-3 receptor expression in the placenta was remarkable. There have been conflicting reports concerning the presence of melanocortin peptides in the placenta as described by Krieger, D. T., Biol. Reprod. 26:55-71 (1982) and Clark, D. et al., Nature 273:163-164 (1978). However, α-MSH levels are known to rise markedly in the maternal circulation in late pregnancy as described by Clark, D. et al., supra, and a switch in sensitivity of the fetal adrenal gland from α-MSH to ACTH has been observed prior to parturition as described by Silman, R. E. et al., Nature 260:716-718 (1976) and Challis, J. R. G. et al., Nature 269:818-819 (1977). Whether the MC3 receptor plays a role in these changes may now be further examined. As the technique of Northern blotting is relatively insensitive in demonstrating low abundance mRNAs, a combination of PCR followed by Southern blotting of the reaction products was used to investigate MC3 receptor expression in several gut tissues and obtained positive signals from the stomach, duodenum, and pancreas. Gantz et al. supra. Although several bands were obtained from the PCR reactions only a single band hybridized on Southern blotting with the MC3 receptor probe.

Melanocortin-4 Receptor.

As discussed above, the members of the melanocortin receptor family can be differentiated on the basis of their tissue distribution. While the MC1 receptor is localized to melanocytes and the MC2 receptor to adrenal cortical cells, the MC4 receptor is found primarily in the brain as shown in FIGS. 1A and 1B. Gantz et al., J. Biol. Chem. 268:15174-15179 (1993). FIGS. 1A and 1B depicts tissue distributions of the MC4 receptor as evidenced by Northern blotting with RNA extracted from various tissues. Furthermore, the blot in FIG. 1A represents 5 μg of canine poly(A⁺) RNA and in FIG. 1B, 35 μg of human total RNA from the tissues listed. In the brain, receptors can be demonstrated by in situ hybridization in regions of the thalamus, hypothalamus, and hippocampus; however, there are distinct differences in the patterns of their expression. The extensive labeling of the MC4 receptor in the CA1 and CA2 regions of the hippocampus is of particular interest in view of the purported central nervous system functions of melanocortins in learning and memory. Notably, the MC4 receptor is not expressed in the placenta (data not shown), a tissue that expresses the MC3 receptor in large amounts.

Melanocortin-5 Receptor.

The tissue distribution of mMC5 receptor is unique among the melanocortin receptors. Using a random primed the mMC5 receptor probe and a mouse/rat multiple tissue Northern (MTN) blot (Clontech, Palo Alto, Calif.), extraordinarily high levels of expression in skeletal muscle and substantial expression in spleen and lung were detected. Gantz, I. et al., "Molecular Cloning Expression and Characteristic of a Fifth Melanocortin Receptor," (unpublished). Of note was the absence of mMC5 receptor in brain tissue, a tissue known to express MC3 receptor and MC4 receptor, and placenta, a tissue which expresses MC3 receptor. Gantz, I. et al., J. Biol. Chem. 268:8246-8250 (1993) and Gantz, I. et al., J. Biol. Chem. 268:15174-15179 (1993). In addition, utilizing the same mMC5 receptor probe under conditions of reduced stringency to accommodate cross-species differences, no expression was observed in the human A375 melanoma cell line, which expresses MC1 receptor, or in either normal or malignant human adrenal cortical tissues, both of which express MC2 receptor. Gantz, I. et al., J. Biol. Chem. 268:8246-8250 (1993) and Gantz, I. et al., J. Biol. Chem. 268:15174-15179 (1993). It is notable, however, that experiments were unable to demonstrate mMC5 receptor expression in any human tissue, (human MTN blot or human MTN blot II, Clontech), including tissues shown to express this receptor in the mouse. Furthermore, so far isolation of an homologous human receptor has been unsuccessful despite three attempts at screening two different human genomic libraries and one human muscle cDNA library using a mMC5 receptor probe. While inconclusive, these data suggest the possibility that there is no counterpart to the mMC5 receptor in man.

SPECIFIC EXAMPLE 3 PHARMACOLOGICAL STUDIES Materials and Methods

Peptide Synthesis.

The following peptides were obtained from Peninsula Laboratories, Inc. (Belmont, Calif.): human and rat ACTH, ACTH(1-10), ACTH(4-10), ACTH (1-13), α-MSH, Nle⁴,D-Phe⁷ !α-MSH, β-MSH, γMSH, des-acetyl! α-MSH, β-endorphin, porcine β-lipotropin, and Met!enkephalin. Substituted melanocortin peptides (Pro¹¹ γMSH, Phe¹ γ-MSH, Thr¹ γMSH, Thr¹,Pro¹¹ γ-MSH)and ACTH (4-13) were synthesized by the University of Michigan Protein and Carbohydrate Structure Facility on an Applied Biosystems Model 431 peptide synthesizer using standard FMOC chemistry.

cAMP Assays.

For these assays a cAMP assay kit (TRK 432, Amersham Corp.) was employed. Cells transfected with the receptors were grown to confluence in 12-well (2.4×1.7 cm) tissue culture plates. The cells were maintained in Dulbecco's modified Eagle's medium (GIBCO) containing 4.5 g/100 ml glucose, 10% fetal calf serum, 100 units/ml penicillin and streptomycin, 1 mM sodium pyruvate, and 1 mg/ml Geneticin. For assays, this medium was removed and cells were washed twice with Earle's balanced salt solution containing 10 mM Hepes (pH 7.4), 1 mM glutamine, 26.5 mM sodium bicarbonate, and 100 mg/ml bovine serum albumin. An aliquot (0.5 ml) of Earle's balanced salt solution was placed into each well along with 5 μl of 2×10⁻² M isobutylmethylxanthine. Varying concentrations of agonist were added, and the cells were incubated to 30 min at 37° C. Ice-cold 30% trichloracetic acid (500 μl/well) was added to stop the reaction and precipitate cellular protein. The cells were scraped and transferred to 16×150-mm glass tubes, then placed on ice for 30 min. The precipitate was then centrifuged for 10 min at 1,900×g, and the supernatant was ether extracted, lyophilized, and resuspended in 50 mM Tris, 2 mM EDTA (pH 7.5). cAMP content was then measured by a competitive binding assay according to the assay instructions. Percent change in intracellular cAMP was calculated using the response of 10⁻⁶ M αMSH as 100% response.

Binding Assays.

Transfected cells were grown to confluence in 2.4×1.7 cm multiwell plates. After removal of media the cells were washed twice with Earle's balanced salt solution (EBSS, Gibco, Grand Island, N.Y.) and incubated for 1 h with 36nCi (1Ci=37GBq) of the ¹²⁵ I-labeled Nle⁴, D-Phe⁷ !α-MSH ( ¹²⁵ I!NDP-MSH) which was prepared according to the protocol of Tatro and Reichlin. Tatro, J. B. et al., Endocrinology 121:1900-1907 (1987). Binding reactions were terminated by removing the media and washing the cells twice with 0.2M sodium phosphate/0.15M NaCl (pH 7.4). The cells were lysed with 1% Triton X-100 and the radioactivity in the lysate was quantified in a liquid scintillation counter. Nonspecific binding was determined by measuring the amount of ¹²⁵ I!NDP-MSH remaining bound in the presence of 10⁻⁵ M unlabeled NDP-MSH and specific binding was calculated by subtracting nonspecifically bound radioactivity from total bound radioactivity.

Results

Melanocortin-3 Receptor.

The pharmacological characteristics of the MC3 receptor demonstrated subtle but significant differences with those of the α-MSH (melanocortin-1) receptor. Both receptors responded to α-MSH and ACTH with equal potency and efficacy as depicted in FIGS. 2A and 2B. In this regard the present investigations are at variance with those of Mountjoy, K. G. et al., Science 257:1248-1251 (1992), who observed that ACTH was less potent and less efficacious than α-MSH in inducing cAMP production via the MC1 receptor. However, the present investigations are consistent with those of Chhajlani, V. et al., FEBS Lett. 309:417-420 (1992), who noted that ACTH and α-MSH had equal affinities in displacing ¹²⁵ I-labeled Nle⁴,D-Phe⁷ !α-MSH from the MC1 receptor. The results of the present studies are shown in FIGS. 2A and 2B. FIGS. 2A and 2B shows the generation of cAMP in L-cells transfected with the MC1 receptor and the MC3 receptor in response to α-MSH, β-MSH, γ-MSH, ACTH(1-39), and Nle⁴, D-Phe⁷ !α-MSH. Each point represents the average of duplicate samples from three different experiments. Standard errors were less than 10% for each point on this figure.

In view of previous structure-function studies indicating that the free NH₂ -terminal serine in the ACTH molecule is an essential requirement for the hormone's full biological activity as described in Garren, L. D., Vitam. Horm. 26:119-141 (1968), the fact that α-MSH (which has an acetylated NH₂ -terminal serine) is as potent and efficacious as ACTH in acting at both the MC1 and MC3 receptors clearly categorizes these two receptors as MSH receptors. The ED₅₀ of ACTH and α-MSH with both receptors, approximately 10⁻⁹ M, is consistent with that observed for MSH receptors in previous pharmacological studies. Responses of the MC1 receptor and the MC3 receptor to des-acetyl! α-MSH, which lacks the acetylated serine at the amino terminus of the peptide were identical to those observed for ACTH and α-MSH (data not shown). In addition, neither the MC1 receptor nor the MC3 receptor responded to the other POMC-derived peptides Met!enkephalin or β-endorphin (data not shown).

A major difference in the pharmacological characteristics of the MC1 and MC3 receptors is in their responses to β- and γ-MSH. Although the MC3 receptor responds to these two peptides as well as it does to ACTH and α-MSH, the MC1 receptor does not, as shown in FIGS. 2A and 2B. β-MSH is fully efficacious in stimulating cAMP production via the MC1 receptor, but its potency is 10-fold lower than that of ACTH and α-MSH. γ-MSH is unable to induce a full cAMP response through the MC1 receptor, even at maximal concentrations. The differences between the MC1 and MC3 receptors in ligand specificity are corroborated in studies with the truncated peptides ACTH(1-10) and ACTH(4-10) as shown in FIGS. 3A and 3B. FIGS. 3A and 3B shows the generation of cAMP in L-cells transfected with the α-MSH (MC1) and the novel melanocortin receptor MC3 in response to ACTH(1-10) and ACTH(4-10). For ease of comparison, the data are presented as percentage of the maximal response to ACTH(1-39). Each point represents the average of duplicate samples from three different experiments. Standard errors were less than 10% for each point in this figure. Because these studies show MC3 receptor appears to recognize ACTH and α-, β-, and γ-MSH equally well, the core heptapeptide is the specific site of the melanocortins that is recognized by the receptor. The observation that ACTH(4-10) and ACTH(1-10) both demonstrated full efficacy in stimulating cAMP production via the MC3 receptor supports this assertion. The lower order potency noted with the truncated peptides reflects that their smaller size gives them somewhat lower affinity for the receptor. In contrast, neither ACTH(1-10) nor ACTH(4-10) were able to induce a full response with the MC1 receptor. Since α-MSH is equivalent to ACTH(1-13), the marked reduction in activity noted with ACTH(1-10) and ACTH(4-10) indicates that both the structures of the amino- and carboxyl-terminal ends of α-MSH are important for full biological activity of the MC1 receptor.

Melanocortin-4 Receptor.

The pharmacological characteristics of this receptor confirm that it is a member of the melanocortin receptor family. As shown in FIG. 4, COS-1 cells transiently transfected with the MC4 receptor gene demonstrated a marked increase in intracellular cAMP content in response to stimulation with both α-MSH and ACTH. It is of note, however, that wild-type COS-1 cells appear to have a small endogenous response to melanocortins. COS-1 cells transfected with the CMV vector containing no insert had a response indistinguishable from that obtained with the wild-type cells. The data in FIG. 4 represents an average of duplicate samples from two different experiments. FIG. 4 shows the generation of cAMP in response to ACTH and α-MSH in wild type COS-1 cells and COS-1 cells transiently transfected with the MC4 receptor gene. Wild type cells have a small endogenous response to the peptides. COS-1 cells transfected with the CMV vector without a receptor insert had a response comparable to the wild type cells. The data in FIG. 4 represents an average of duplicate samples from two different experiments.

For further examination of the pharmacological characteristics of the MC4 receptor, its gene was permanently transfected into L-cells, a murine fibroblast cell line, which demonstrate no endogenous response to melanocortins. FIG. 5 shows generation of cAMP in L-cells transfected with the MC4 receptor gene. Responses to α-, β-, and γ-MSH, ACTH(1-10) and ACTH(4-10) (n=3 separate experiments) were measured. Each point represents the average of the total number of experiments obtained with each agonist. Standard errors were less than 12% for each point. As shown in FIG. 5, in the transfected cells, ACTH and α-MSH elicited a dose-dependent increase in intracellular cAMP content with equal potency and efficacy. The equipotence of α-MSH and ACTH in stimulating MC4 receptors is identical with the responses observed in L-cells transfected with the genes encoding the MC1 and MC3 receptors. The observed half-maximal effect of the two ligands (EC₅₀ =10⁻⁹ M) is consistent with previously published pharmacological studies of melanocortin receptors. Like the MC1 and MC3 receptors, the MC4 receptor did not respond to the other pro-opiomelanocortin-derived peptides Met-enkephalin or β-endorphin although a small increase in cAMP was observed after stimulation with β-lipotropic.

Despite these similarities, the MC4 receptor demonstrates subtle but important pharmacological differences from the other melanocortin receptors which could be elicited with the various ligands depicted in FIG. 6. In FIG. 6 the core heptapeptide amino acids are boxed. As discussed above, the MC3 receptor recognizes the ACTH(4-10) core of the melanocortins, thus it responds with equal potency and efficacy to α-, β-, and γ-MSH and ACTH. In contrast, γ-MSH is unable to stimulate a full cAMP response via the MC1 receptor, and the potency of β-MSH at this receptor is 10-fold lower than that for a α-MSH and ACTH. Accordingly, the specificity of the MC1 receptor appears to depend on amino acid residues that extend in the carboxyl- and amino-terminal directions from the ACTH(4-10) core. This conclusion was supported by the observation that the truncated peptides ACTH(1-10) and ACTH(4-10) were fully efficacious agonists on MC3 receptors but not on MC1 receptors. In this respect, the MC4 receptor more closely resembles the MC1 receptor as shown in FIG. 5. One key difference between MC4 and MC1 receptors, however, is that β-MSH is equipotent with ACTH and α-MSH in acting on the former but not the latter. This observation implies that a portion of the β-MSH molecule at the carboxy-terminal extension beyond the ACTH(4-10) core can determine the selectivity between MC1 and MC4 receptors. Structural analysis of FIG. 6 shows Pro¹² of ACTH, which is shared by α-MSH and ACTH but not by γ-MSH, is critical for binding as a full agonist to the MC4 receptor. Because γ-MSH has a Phe substitution in the position corresponding to Pro¹² of ACTH, it is a less potent agonist than ACTH or α-MSH. The tyrosine (Tyr²) residue of ACTH is also important in defining activity at the MC4 receptor inasmuch as γ-MSH and ACTH(1-10) appear to have slightly greater efficacy than ACTH(4-10) which is lacking this amino acid residue. These findings may have implication for the design of specific agonists or antagonists for the MC4 receptor.

Further Studies on the Melanocortin-3 and Melanocortin-4 Receptors.

To test the hypothesis that the proline (Pro¹²) in the C-terminal portion of ACTH/α-MSH was a key determinant of melanocortin activation of the MC4 receptor, a γ-MSH-like peptide was synthesized that substituted the phenylalanine (Phe¹¹) present in the C-terminal portion of γ-MSH with a proline (Pro¹¹). As represented in FIG. 6 (See also Sequence Listing ID NOS. 13-23), Pro¹¹ of γ-MSH is equivalent to the Pro¹² of ACTH/α-MSH. If the Pro¹² of ACTH/α-MSH was of key importance for the activation of the MC4 receptor by substituting the Phe¹¹ of that molecule with proline should increase the activity of γ-MSH at this receptor. γ-MSH was chosen as the melanocortin to be altered because it has full agonist activity at the MC3 receptor, but is only a weak agonist at the MC4 receptor. In addition, as already noted, γ-MSH contains two substitutions of the common melanocortin heptapeptide sequence which may render it more informative for investigating the hypothesis that the core sequence is of lesser importance to the activation of the MC4 receptor. Conversely, if the MC3 receptor is activated predominantly by amino acids present in the melanocortin core heptapeptide sequence, then the substitution of this Phe¹¹ (which is outside the core heptapeptide sequence) with Pro¹¹ should not result in any significant diminution of the activity of the substituted Pro¹¹ γ-MSH when compared to γ-MSH at that receptor. Consistent with this reasoning, as shown in FIG. 7A, wherein each point represents the average of 3-6 separate experiments, substitution of Phe¹¹ of γ-MSH with proline had no significant effect on the activation of MC3 receptor. As shown in FIG. 7B, substitution of Phe¹¹ of γ-MSH with proline profoundly increased the activity of γ-MSH at the MC4 receptor. Using the dose response curve of α-MSH as a reference for maximum response, the potency of the Pro¹¹ γ-MSH in comparison to γ-MSH was increased nearly a log (from an EC₅₀ of 2×10⁻⁸ M to 1×10⁻⁷ M) and the efficacy of Pro¹¹ γ-MSH in comparison to γ-MSH was increased from 45% (γ-MSH) to 75% (Pro¹¹ γ-MSH-like peptide). This was consistent with the hypothesis that the proline moiety present in the carboxyl terminal portion of melanocortins is a structural component specifically important to the activation of the MC4 receptor as opposed to the MC3R.

To investigate the contribution of amino acids in the N-terminal portion of the melanocortin peptides to the activation of the MC3 and MC4 receptors, a tyrosine residue (Tyr²) in the N-terminal portion of ACTH/α-MSH was focused on. As already stated, the greater activity of ACTH (1-10) than ACTH (4-10) at the MC4 receptor suggested a contribution of this amino acid, which is conserved in all the melanocortins, to the activation of this receptor. If the hypothesis regarding the contribution of this tyrosine to the activation of the MC4 receptor was correct, then any alteration of this amino acid should diminish the activity of a peptide containing a tyrosine substitution at this receptor. Since it was already demonstrated that the Pro¹¹ γ-MSH compound had increased activity as compared to γ-MSH at the MC4 receptor (but not the MC3 receptor) two tyrosine substitutions in the Pro¹¹ γ-MSH peptide were designed. These two substitutions consisted of an exchange of the Tyr¹ of Pro¹¹ γ-MSH (which is analogous to the Try² of ACTH/α-MSH, see FIG. 6) with a phenylalanine (Phe¹) or a threonine (Thr¹). These substitutions were an attempt to examine the major component groups of the amino acid tyrosine, a phenol ring and an hydroxyl group. As shown in FIG. 7B, substitution of Tyr² by either phenylalanine or threonine diminished both the potency and efficacy of these substituted compounds at the MC4 receptor as compared to the Pro¹¹ γ-MSH. This was consistent with the hypothesis that Try² of ACTH/α-MSH is important for the activation of the MC4 receptor. However, since the Phe¹, Pro¹¹ γ-MSH had greater activity than γ-MSH or Thr¹, Pro¹¹ γ-MSH, even though its activity was only intermediate between these compounds, it was concluded that the phenylalanine ring of the tyrosine residue has a more significant role than the hydroxyl group. Conceivably, the activity of the phenylalanine moiety could be attributed to its bulky and/or hydrophobic properties.

As shown in FIG. 7A, the diminished activity of the tyrosine substituted Pro¹¹ γ-MSH peptides at the MC3 receptor suggests that this tyrosine moiety is also important to the activation of the MC3 receptor. Therefore, the equipotence of the various melanocortin peptides at the MC3 receptor is due to this conserved tyrosine residue in addition to the amino acids of the shared heptapeptide core as was originally hypothesized.

The contribution of both the proline in the C-terminal and the tyrosine in the N-terminal portions of the melanocortins to the activation of the MC3 and MC4 receptors using several truncated peptides was further examined. The truncated peptide ACTH (4-13) which contains the C-terminal proline shown to be important for the activation of the MC4 receptor but which lacks the biologically active N-terminal tyrosine necessary for the full activation of both receptors was synthesized and the activity of this synthetic peptide with ACTH (1-10), ACTH (4-10), and ACTH (1-13) was compared. As expected, ACTH (1-13) had maximal efficacy at both the MC3 and MC4 receptors. These results are depicted in FIGS. 8A and 8B wherein each point represents the average of 3-6 experiments. However, as shown in FIG. 8B, the efficacy of ACTH (1-10) or ACTH (4-10) which lack the C-terminal proline was only 30% of that of ACTH (1-12) at the MC4 receptor. In contrast, the efficacy of ACTH (4-13) which contains the critical proline moiety was increased to 60% of the maximal response of ACTH (1-13). Thus, ACTH (4-13) is twice as efficacious as of either ACTH (1-10) or ACTH (4-10) at the MC4 receptor. At the same time, the efficacy of ACTH (1-13), ACTH (1-10), ACTH (4-10), and ACTH (4-13) are nearly the same at the MC3 receptor as shown in FIG. 8A. These data support the contention that the melanocortin core heptapeptide sequence is a key element responsible for conferring full efficacy to these peptides at the MC3 receptor. Since, as shown in FIG. 7A, α-MSH, γ-MSH (which lacks a C-terminal Pro), and Pro¹¹ γ-MSH are equipotent at the MC3 receptor, the increased order of potency of the truncated peptides (ACTH (1-13)>>ACTH (1-10) which is roughly equivalent to ACTH (4-13)>ACTH (4-10)) is interpreted to be due to the increasing size (in terms of increasing length) of these truncated peptides rather than to the presence or absence of the C-terminal proline or N-terminal tyrosine. This increase in length may confer greater affinity for the peptides at the MC3 receptor. In contrast, the equal and lesser potency of both ACTH (1-10) and the smaller peptide ACTH (4-10) when compared to the greater potency of ACTH (4-13) (which is the same number of amino acids as ACTH (1-10)) suggests that it is the C-terminal proline of ACTH/αMSH rather than peptide size alone that is the dominant factor in determining the activity of the truncated peptides at the MC4 receptor.

Finally, whether the presence of an acetylated N-terminal serine affects the activity of the melanocortins at either the MC3 or MC4 receptor was examined. Previous literature has suggested an acetylated serine is critical for the activity of ACTH at the MC2 receptor (adrenal ACTH receptor). Garren, L. D., Vitam. Horm. 26:119-141 (1968). As shown in FIGS. 9A and 9B, wherein each point represents the average of 3-6 experiments, no difference was observed between the activity of α-MSH which has an acetylated amino terminal serine and des-acetyl α-MSH (ACTH (1-10)) which lacks this acetyl group at both the MC3 and MC4 receptors.

In summary, the studies indicate that the proline residue present in the C-terminal portion of the melanocortin peptide sequence constitutes a crucial element underlying the selective pattern of response of the MC3 and MC4 receptors for the melanocortins. A tyrosine present in the N-terminal portion of the melanocortin peptides is necessary for the full activation of both the MC3 and MC4 receptors. Finally, the core heptapeptide sequence is essential to the activation of the MC3 receptor but is of lesser importance to the activation of the MC4 receptor. These results indicate a model of activation of the MC3 and the MC4 receptors by the melanocortins which could metaphorically liken these peptides to a "donut and its hole." The "donut" portion of melanocortins containing the N-terminal tyrosine and C-terminal proline residues is required for activation of the MC4 receptor whereas the "hole" the amino acids present in the core heptapeptide sequence of the melanocortins, is of much greater importance in the activation of the MC3 receptor. Information derived from these studies using substituted peptides provides a basis for the development of subtype specific melanocortin agonists and antagonists.

Melanocortin-5 Receptor.

The pharmacological profile of the mMC5 receptor is unique in that α-MSH is clearly more potent than ACTH in stimulating the production of intracellular cAMP in L-cells expressing the receptor. These results are represented in FIG. 10 where each point represents the average of 3 separate experiments and standard errors were less than 10% for each point. Rat ACTH, which differs from human ACTH in two amino acids produced the same results. Those data contrast with previous studies demonstrating that α-MSH and ACTH are equipotent in stimulating cAMP production by other human melanocortin receptors (MC1, MC3, and MC4 receptors) expressed in the same cell line. Gantz, I. et al., J. Biol. Chem. 268:8246-8250 (1993) and Gantz, I. et al., J. Biol. Chem. 268:15174-15179 (1993). Mountjoy, et al. have reported, however, that α-MSH is more potent than ACTH in stimulating cAMP production via the mMC1 receptor. Mountjoy, K. G. et al., Science 257:1248-1251 (1992). It is possible that the ability to differentiate between α-MSH and ACTH is a property unique to murine melanocortin receptors. In this regard, it is important to note the structural differences between α-MSH and ACTH (1-39). Although the amino acid sequence for the first 13 amino acids of ACTH is identical to that of α-MSH, ACTH (1-39) is not acetylated at its amino terminal end in the manner of α-MSH. Thus, the possibility that the ability of mMC5 receptor to distinguish between α-MSH and ACTH (1-39) might be dependent on the presence or absence of the amino terminal acetyl moiety, was examined. However, no difference between non-acetylated α-MSH ((ACTH (1-13)) and α-MSH in stimulating cAMP production in transfected cells was observed. Other studies examined whether the ability of the mMC5 receptor to distinguish between α-MSH and ACTH (1-13) on the one hand and ACTH (1-39) on the other occurs at the level of the receptor or reflects a post-receptor signaling phenomenon. These results are depicted in FIG. 11 wherein each point represents the average of 3 experiments and standard errors were less than 10% for each point. The former mechanism is supported by the results which indicated that the binding affinity of the mMC5 receptor for α-MSH and ACTH (1-13) appeared to be ten-fold greater than that for ACTH (1-39). These data imply that the mMC5 receptor does not distinguish between amino terminally acetylated or non-acetylated ACTH/α-MSH compounds and, thus, that the carboxyl terminal extension of ACTH (1-39), (ACTH (14-39)) must be the determinant of its diminished potency relative to α-MSH or ACTH (1-13). In addition, since a free non-acetylated amino terminus is an essential requirement for the ability of ACTH to induce steroidogenesis in the adrenal cortex (Garren, L. D., Vitam. Horm. 26:119-141 (1968)), the mMC5 receptor appears primarily not to be an ACTH receptor.

Further studies were performed to characterize the ligand specificity of the mMC5 receptor. As shown in FIG. 10, both β- and λ-MSH were full agonists, but were one and three orders of magnitude lower in potency, respectively, than α-MSH. The central core heptapeptide (ACTH (4-10)) common to all melanocortins had essentially no biological activity as shown in FIG. 11. Neither were the other products of pre-opiomelanocortin processing, β-endorphin, met-enkephlin, or porcine β-lipotropin active on the mMC5 receptor (data not shown). However, α-MSH peptides which contain an amino (ACTH (1-10)) or carboxyl (ACTH (4-13)) terminal extension had full efficacy albeit with greatly diminished potency relative to α-MSH in inducing cAMP production in L-cells transfected with the mMC5 receptor, as shown in FIG. 12. The structure-function studies indicate that amino acids in both the carboxyl and amino terminal extension regions (relative to the heptapeptide core) of α-MSH are critical determinants of agonist activity at the mMC5 receptor. A comparison of the various ligands tested, the non-substituted peptides shown in FIG. 6 and ACTH (1-39), in conjunction with data herein suggests the possibility that Tyr² and Pro¹² of α-MSH are particularly important in this regard. The lack of activity of ACTH (4-10) and the full efficacy of α-MSH imply that the core heptapeptide may be important as a spacer between amino and carboxyl terminal extensions, but the specific sequences may be a less important factor in the binding of melanocortins to the mMC5 receptor. In this regard the mMC5 receptor resembles the MC4 receptor more closely than the other members of the melanocortin receptor family. Gantz, I. et al., J. Biol. Chem. 268:15174-15179 (1993).

SPECIFIC EXAMPLE 4 INTRACELLULAR SIGNALING PATHWAYS Materials and Methods

Receptor Gene Expression.

The coding region of the MC3 receptor gene was subcloned into the eukaryotic expression vector CMVneo using a polymerase chain reaction (PCR) strategy as previously described. Brown, N. A. et al., et al., J. Biol. Chem. 265:13181-13189 (1990) and Gantz, I. et al., PNAS (USA) 88:429-433 (1991). The insert was subsequently checked by dideoxynucleotide sequencing to insure that no errors were induced by the PCR. A rat hepatoma cell line (Hepa) which lacks endogenous melanocortin receptors was transfected with the CMVneo/MC3 receptor construct using the calcium phosphate co-precipitation method. Chen, C. A. et al., Biotechniques 6:632-638 (1988). Cells were selected for resistance to the neomycin analogue Geneticin (Life Sciences) and clones were subsequently chosen for high levels of receptor mRNA expression by Northern blot analysis.

Chimeric Receptor.

For these studies a chimeric canine H2-histamine receptor (cH2R) in which the third intracytoplasmic loop (3i) of the MC3 receptor was substituted for the comparable segment of cH2R was expressed. The chimeric receptor (cH2R/MC3R-3i) was constructed by cassette mutation at the junction of the fifth and sixth transmembrane domains of cH2R. Six PCR primers were used to generate three DNA fragments which were subsequently ligated together. The three PCR-generated fragments consisted of 1) the 5' coding region of the cH2R receptor beginning just prior to the ATG codon and ending with the 3' end of the fifth transmembrane domain; 2) the portion of the MC3 receptor gene encoding its third intracytoplasmic loop; and 3) the 3' coding region of the cH2R beginning with that segment encoding the 5' end of the sixth transmembrane domain and ending slightly past the termination codon. The DNA fragments were cut with appropriate restriction enzymes at pre-engineered restriction sites designed so that the three fragments could be assembled together in only the correct alignment. Restriction sites were also designed to facilitate subcloning the chimeric receptor DNA into CMVneo and the sequencing vector M13. The nucleotide sequence of the CMVneo cH2PJMC3R-3i construct was confirmed prior to expression in Hepa cells.

cAMP Assays.

A cAMP assay kit purchased from Amersham (TRK 432, Arlington Heights, Ill.) was employed. Transfected cells were grown to confluence in 12-well (2.4×1.7 cm) tissue culture plates. The cells were maintained in Dulbecco's modified Eagle's medium (DMEM, Gibco) containing 4.5 g/100 ml glucose, 10% fetal calf serum, 100 units/ml penicillin and streptomycin, 1 mM sodium pyruvate and 1 mg/ml of Geneticin. For assays, the media was removed and cells were washed twice with Earle's balanced salt solution (EBSS) containing 10 mM Hepes (pH 7.4), 1 mM glutamine, 26.5 mM sodium bicarbonate, and 100 mg/ml bovine serum albumin. An aliquot (0.5 ml) of EBSS was placed into each well along with 5 μl of 1×10⁻² M isobutylmethylxanthine. Varying concentrations of agonists (human ACTH (1-39) and α-MSH, Peninsula Laboratories, Belmont, Calif.) were added and the cells were incubated for 30 min at 37° C. Ice cold 100% ethanol (1 ml/well) was added to stop the incubation and the mixture including scraped cells was transferred to 16×150 mm glass tubes, placed on ice for 30 min, then centrifuged for 10 min at 1,900×g. The supernatant was dried under a nitrogen stream, and resuspended in 50 mM Tris, 2.0 mM EDTA (pH 7.5). cAMP content was then measured by competitive binding assay according to the assay instructions. In some experiments cells were pre-treated for 30 min prior to agonist stimulation with the cAMP-dependent protein kinase (protein kinase A) inhibitor N- 2-(p-bromocinnamyl-amino)ethyl!-5-isoquinolinesulfonamide (H-89, Calbiochem, La Jolla, Calif.) or with H-85 (Seikagaku America, Rockville, Md.), an isoquinolone derivative with no inhibitory activity on protein kinase A. Forskolin and dibutryl cAMP were added simultaneously with the agonists in these experiments.

Inositol Phosphate (IP)Assays.

Measurement of inositol phospholipid turnover in Hepa cells was performed according to a modification of previously published methods as follows. Berridge, M. J. et al., Biochem J. 212:473-482 (1983) and Wreggett, K. A. et al., Biochem. J. 245:655-660 (1987). Cells grown to semi-confluence in multiwell plates were prelabeled with 2-³ H! myo-inositol in DMEM for 24 hr, incubated in EBSS for 30 min, then incubated for another 15 min in EBSS with 10 mM LiCl. The final incubation was in media with experimental ligand added for up to three min after which ice cold 100% methanol was added and the cells were scraped and extracted with 2 ml chloroform, 10 μl HCl (13N), and 200 μl of 100 mM EDTA in a 50 ml polypropylene tube. The mixture was then vortexed and centrifuged at 1,900×g. The supernatant was removed and its pH was adjusted to 7.0 by adding 1N NaOH. Waters Accel plus QMA SEP-PAK anion exchange cartridges (Waters Chromatography, Millipore Corporation, Milford, Mass.) were used to separate inositol phosphates under differing concentrations of formate/formic acid. The cartridges were pretreated by washing with 10 ml of a solution of 1M ammonium formate in 0.1M formic acid followed by 20 ml of distilled water. The samples were applied with a flow rate of approximately 10 ml/min using a 10 ml syringe. IPs were then eluted using 10 mM increments of ammonium formate in a stepwise fashion. Inositol monophosphate was eluted with 10 mM formic acid/100 mM ammonium formate/5 mM disodium tetraborate, inositol bisphosphate was eluted with 20 mM formic acid/200 mM ammonium formate/5 mM disodium tetraborate, and IP3 was eluted with 30 mM formic acid/300 mM ammonium formate/5 mM disodium tetraborate. This assay does not distinguish between 1,3,4 and 1,4,5 isomers of IP3. Eluted radioactivity from the pooled fractions (total inositol phosphates) were measured by liquid-scintillation spectrometry (Beckman model LS7800 instrument).

Measurement of Intracellular Ca++ Concentration ( Ca++!i).

For these experiments, Hepa cells were detached by incubation in Ca⁺⁺ -free EBSS with 2.0 mM EDTA, loaded with 1 μM fura-2/AM (Molecular Probes, Eugene, Oreg.) for 20 min at 37° C. in EBSS containing 0.1% BSA and 25 mM HEPES, washed by centrifugation at 50×g, and resuspended and maintained in EBSS buffer at room temperature until the time of experimentation. Ca⁺⁺ !i measurements of cells suspended in a quartz cuvette were obtained using a dual-wavelength modular fluorometer (Spex-Fluorolog 2, Spex Industries, Edison, N.J.) according to previously described methods. DelValle, J. et al., Am. J. Physiol. 262:G420-426 (1992).

Results

Both ACTH and α-MSH stimulated cAMP production in Hepa cells transfected to express the MC3 receptor. These results are depicted in FIGS. 13A and 13B wherein the cells were pre-labeled with 2-³ H! myo-inositol and wherein each point represents the average of three experiments with standard error (SE),<10%. Neither peptide had any effect on non-transfected Hepa cells. The stimulatory effect was dose-dependent and monophasic, and cAMP production ultimately exceeded 15 times the control unstimulated levels at maximal doses of hormone. When the effects of ACTH and α-MSH on inositol phospholipid turnover were examined, a remarkably different pattern was observed. At low doses (below 10⁻¹¹ M) there was a clear stimulatory effect, however, at higher doses, there was a dose dependent inhibitory effect. Maximal stimulation of ³ H!-IP production reached only 155% of basal unstimulated value. To confirm these observations, the time dependent production of ³ H!-IP3 was examined in cells pre-labeled with 2-³ H! myo-inositol. As shown in FIG. 14, wherein each point represents the average of three experiments with standard error (SE)<10%, there was a rapid initial phase of IP3 production achieved within 5 seconds of exposure to ligand followed by a rapid decrease then a secondary gradual increase. The initial peak is attributable to the production of inositol 1,4,5 trisphosphate while the secondary rise may reflect other events such as the production of inositol 1,3,4 trisphosphate from inositol tetrakisphosphate. The initial phase of the IP3 response was dose-dependent, reaching maximum levels at α-MSH concentrations of 10⁻¹⁰ M but decreasing in magnitude beyond that dose.

In pursuing the mechanism for the unique differences between the dose-response curves for agonist induced increases in cAMP content and inositol phospholipid turnover in cells transfected with MC3 receptor, the possibility that the two post-receptor events might be linked in some way was examined. Toward this end, the effect of exogenously administered forskolin, a direct stimulant of adenylate cyclase, and the cell-permeable cAMP analogue, dibutryl cAMP (dbcAMP), on peak ³ H!-IP generation achieved at a dose of 10⁻¹¹ M α-MSH was examined. As shown in FIG. 15, wherein each point represents the average of three experiments with standard error (SE)<10%, both forskolin and dbcAMP dose dependently inhibited the level of ³ H!-IP turnover in response to α-MSH. These data suggested that activation of the adenylate cyclase/cAMP post-receptor signaling cascade, which ultimately results in protein kinase A activation, has an inhibitory effect on inositol phospholipid turnover activated via MC3 receptor. To test this hypothesis further, the effect of the selective protein kinase A inhibitor H-89 (Chhajlani, T. et al., J. Biol. Chem. 265:5267-5272 (1990)) on ³ H!-IP production by α-MSH at doses of 10⁻⁸ M was examined. This dose of α-MSH resulted in ³ H!-IP production which is significantly lower than that observed with 10⁻¹¹ M α-MSH. As shown in FIG. 16A, wherein each point represents the average of three experiments with standard error (SE)<10%, H-89 pretreatment in conjunction with 10⁻⁸ M α-MSH resulted in the restoration of the higher levels of ³ H!-IP products observed with 10⁻¹¹ M α-MSH. This effect of H-89 was dose-dependent reaching a maximum effect at 1 μM and its specificity is indicated by the observation that it was not reproduced by H-85, another isoquinoline compound known to have no effect on protein kinase A. Pretreatment with H-89 converted the biphasic dose response curve for ³ H!-IP generation by α-MSH into a more conventional monophasic dose-response curve as observed for cAMP generation as shown in FIG. 16B, wherein each point represents the average of three experiments with standard error (SE)<10%. This data suggests that protein kinase A activation induced by α-MSH acting on MC3 receptor results in inhibition of membrane inositol phospholipid turnover induced by the same ligand acting at the identical receptor.

As IP3 is known to induce the mobilization of Ca⁺⁺ from intracellular stores the ability of α-MSH to increase Ca⁺⁺ !i in the transfected cells was examined. The low doses of α-MSH below 10⁻¹⁰ M which produced the greatest increase in IP3 generation was anticipated to produce the largest increases in Ca⁺⁺ !i. Nevertheless, no effect of α-MSH on Ca⁺⁺ !i was observed even though the Hepa cells demonstrated an increase in Ca⁺⁺ !i upon stimulation of their endogenous vasopressin receptors. However, pre-treating the cells with H-89 demonstrated a clear increase in Ca⁺⁺ !i. These results are depicted in FIGS. 17A, 17B and 17C, wherein the initial Ca⁺⁺ !i peaks, rather than the plateau phase of the stimulated Ca⁺⁺ !i responses, were used for this analysis. More specifically, FIG. 17A depicts the effect of αMSH (10⁻⁶ M) and vasopressin (10⁻⁷) on H-89 pretreated cells in medium containing 1.8 mMca⁺⁺, FIG. 17B depicts the same in Ca⁺⁺ free medium and EDTA, and FIG. 17C depicts the dose dependency of αMSH induced increases in Ca⁺⁺ !i in the presense or absence of H-89 pre-treatment. These figures further demonstrate that there was an initial peak in Ca⁺⁺ !i followed by a lower but sustained elevation. Although the plateau phase was abolished in Ca⁺⁺ -free incubation conditions, the initial phase was not, indicating that it was dependent on mobilization of Ca⁺⁺ from intracellular stores. These data imply that in addition to inhibition of IP3 generation, protein kinase A activation may also inhibit IP3 mediated increases in Ca⁺⁺ !i.

The unique nature of the interaction between the dual signaling pathways activated by ligand action at the MC3 receptor suggests that it may be mediated by a novel interaction between the receptor protein and the various G-proteins involved in post-receptor events. In studies with other G-protein linked receptors the third intracytoplasmic loop (3i) has been shown to be important in the signaling mechanism. Caron, M. G. et al., J. Biol. Chem. 263:4993-4996 (1988). Accordingly, the possibility that MC3R-3i is a determinant in the observed biphasic pattern of the inositol phospholipid turnover induced by α-MSH was examined. For these studies, a chimeric H2-histamine receptor with the 3i portion of the MC3 receptor inserted in place of cH2R-3i was used. As previously noted and as shown in FIG. 18, the wild-type H2-histamine receptor demonstrated monophasic dose-dependent increases in both cAMP and ³ H!-IP production in response to histamine stimulation, In contrast, the chimeric H2-histamine receptor demonstrated signaling properties more characteristic of the MC3 receptor with a monophasic cAMP dose-response curve, but a biphasic dose-response curve for ³ H!-IP production. As in the case of the MC3 receptor the inhibitory phase of the latter dose response curve was abolished by pretreatment with H-89. Thus, the 3i portion of the MC3 receptor appears to be responsible for conferring the unusual biphasic property to the effect of α-MSH on inositol phospholipid turnover in transfected Hepa cells.

The capacity of a cloned receptor to couple to both cAMP and inositol phospholipid/Ca⁺⁺ mediated signal transduction cascades has been observed previously with numerous members of the superfamily of seven transmembrane G-protein linked receptors including H2-histamine (DelValle, J. et al, Am. J. Physiol 263:420-426 (1992)), muscarinic (m1-m4) (Peralta, E. G. et al., Nature 334:434-437 (1988)), adrenergic (Cotecchia, S. et al., J. Biol. Chem. 265:63-69 (1990)), luteinizing hormone (Gudermann, T. et al., J. Biol. Chem. 267:4479-4488 (1992)), thyroid stimulating hormone (Van Sande, J. et al., Mol. Cell. Endocrinol. 74:R1-R6 (1990)), calcitonin (Chabre, O. et al., Mol. Endocrinol. 6:551-555 (1992)), tachykinin (Nakajima, Y. et al., J. Biol. Chem. 267:2437-2442 (1992)), and glucagon (Jelinek, L. J. et al., Science 259:1614-1616 (1993)) receptors. Indeed, while these receptors all demonstrate one predominant signal transduction pathway, the ability to couple to multiple pathways via a single receptor appears to be a relatively common feature of this class of membrane receptors even though the physiological significance of this property is unclear. One concern with the observation of dual signaling by cloned receptors expressed in heterologous cells is that it might represent an artifact of transfection, perhaps resulting from an unusual interaction of the foreign receptor with the endogenous signal transduction machinery of the host cell or to over-expression of the cloned receptor in the presence of limited machinery for linkage to any single signaling system. In the case of MC3 receptor, the physiological nature of the dual signaling linkage is supported by similar observation made on the effects of ACTH on cultured adrenal cortical cells (Woodcock, E. A., Mol. Cell Endo. 63:247-253 (1989) and Buffey, J. et al., J. Endocrinol. 133:333-340 (1992)) presumably via the ACTH receptor (MC2 receptor). Others have noted the same biphasic IP3 and calcium responses at identical agonist doses. Farese, R. V. et al., Biochem. Biophys. Res. Comm. 135:742-748 (1986). Although experiments were performed using primary cultured cells, thus making it impossible to implicate a single receptor class unequivocally, expression of only MC2 receptor in adrenal cortical cells has been identified. The biphasic nature of the inositol phospholipid response noted by MC2 receptor in these studies and by MC3 receptor in the studies herein, coupled with preliminary evidence that the same property is shared by the MC4 receptor (Konda, Gantz, and Yamada unpublished) indicates that it may be an unique characteristic of the melanocortin receptor family of seven transmembrane G-protein linked receptors.

These experiments resulted in a highly unusual divergence in the dose-response curves for MC3 receptor-mediated cAMP generation and membrane inositol phospholipid turnover. The data are consistent with the notion that the production of IP3 induced by MC3 receptor activation is regulated by a protein kinase A mediated phosphorylation event. The exact target for phosphorylation has not been determined from these experiments. One possibility is that phosphorylation of the receptor itself occurs resulting in selective "desensitization" of the inositol phosphate response. Hausdorff, W. P. et al., FASEB J. 4:2881-2889 (1990) However, a consensus phosphorylation site (Kennelly, P. J. et al., J. Biol. Chem. 266:1555-1558 (1991 )) in the 3i of the MC3 receptor which appears to be capable of conferring the biphasic dose-response curve for IP3 production to the chimeric cH2R/JMC3R-3i has not been identified. Nevertheless, this observation does not exclude the possibility that a consensus protein kinase A phosphorylation site elsewhere on the MC3 receptor (or cH2R) might influence the structural conformation of the 3i and thus alter its linkage to the specific G-protein responsible for inducing inositol phospholipid turnover. Equally plausible from these results is that phosphorylation of a protein quite remote from the receptor such as the G-protein complex or phospholipase involved in IP3 generation (Rhee, S. G. et al., "Advances in Second Messenger and Phosphoprotein Research," (Brown, B. L. and Dobson, R. M. eds) Vol. 28, pp. 57-64 (Raven Press, New York 1993)) accounts for the biphasic dose-response curve. The observation that even in the presence of increased IP3 production, such as seen at the 10⁻¹¹ M dose of α-MSH, no increase in Ca⁺⁺ !i was induced unless the transfected cells were pre-treated with H-89 suggest that the IP3 receptor may also be a target for protein kinase A phosphorylation. Rhee, S. G. et al., "Advances in Second Messenger and Phosphoprotein Research," (Brown, B. L. and Dobson, R. M. eds) Vol. 28, pp. 57-64 (Raven Press, New York 1993) The physiologic significance of the divergent effects of the MC3 receptor on cAMP generation and IP3 production has yet to be determined. However, the observation that ACTH has an inhibitory effect on angiotensin II stimulated inositol phospholipid turnover in adrenal glomerulosa cells (Woodcock, E. A., Mol. Cell Endo. 63:247-253 (1989)) suggests that the effect of protein kinase A activation by melanocortin receptors on IP3 generation may extend beyond the boundary between separate receptors on the same cell.

SPECIFIC EXAMPLE 5 CHROMOSOME LOCALIZATION Materials and Methods

Chromosome Localization.

Chromosome localization was performed with assistance of the University of Michigan Genome Center using the fluorescent in situ hybridization (FISH) technique according to a modification of the protocols of Pinkel, D. et al., PNAS (USA) 83:2934-2938 (1986), Lichter, P. et al., Science 247:64-69 (1990), and Lemieux, N. et al., Cytogenet. Cell Genet. 59:311-312 (1992). Metaphase chromosomes from a normal female were prepared from peripheral blood lymphocytes following overnight synchronization with 5-bromodeoxyuridine and thymidine release. Cells were harvested and slides were prepared using standard cytogenetic techniques. EMBL3 phage containing genomic inserts of between 10 and 20 kilobases of DNA surrounding and including the melanocortin receptor sequences were biotinylated using a Bionick kit (Life Technologies Inc.). Unincorporated nucleotides were removed using a Sephadex G-50 column. An aliquot (330 ng) of biotinylated DNA was precipitated with 3 μg of Cot-1 DNA and 7 μg of herring testes DNA and resuspended in 10 μl of hybridization mixture (50% formamide/2×SSC/10% dextran sulfate). The probe was denatured for 5 min at 70° C. and preannealed for 15 min at 37° C. Slides were pretreated with RNase and proteinase K and fixed with 4% paraformaldehyde. They were then denatured in 70% formamide, 2×SSC (pH 7.0) for 5 min, followed by dehydration in an ice-cold ethanol series. The preannealed probe mixture was applied to the denatured slide under a sealed 22-mm square coverslip, placed in a moist chamber, and incubated overnight at 37° C. Post-hybridization washed were at 37° C. in 50% formamide, 2×SSC (pH 7.0), followed by washes in 0.1×SSC at 42° C., and a final wash of 4×SSC at room temperature. Slides were preblocked with 4×SSC, 3% bovine serum albumin for 60 min at 37° C. Signal detection was achieved by incubations of 30 min at 37° C. with fluorescein goat antibiotin and fluorescein-labeled anti-goat IgG (Vector, Burlingame, Calif.) in 4×SSC/0.1% Tween/1% bovine serum albumin. Each incubation was followed by washes in 4×SSC/0.1% Tween at 37° C. Slides were counterstained with propidium iodide, rinsed in phosphate-buffered saline (2.68 mM potassium chloride, 1.76 mM anhydrous monobasic potassium phosphate, 137 mM sodium chloride, 10 mM anhydrous dibasic sodium phosphate) and coverslipped with PPD11 anti-fade solution (100 mg of p-phenylenediamine free base diluted in 100 ml of 9 parts glycerol to 1 part phosphate-buffered saline, adjusted to pH 11.0 with 1M NaOH, and stored at -20° C.). Photographs were taken on Kodak ASA 400 Gold film using a Zeiss Axioskop epifiuorescence microscope equipped with a Zeiss filter set allowing simultaneous visualization of fluorescein isothiocyanate and propidium iodide.

Results

The gene encoding the MC4 receptor was localized by fluorescent in situ hybridization to chromosome 18(q21.3). Gantz et al., J. Biol. Chem. 268:15174-15179 (1993). Other genes localized to this site include those encoding the protooncogene oncogene bcl-2 (Tsujimoto, Y. et al., PNAS (USA) 83:5214-5218 (1986)) and plasminogen activator inhibitor type II (Samia, J. A. et al., Genomics 6:159-167 (1990)), neither of which has any relationship to G-protein-linked receptors. The gene encoding the MC2 receptor gene is found on the opposite arm of the same chromosome, 18 (p11.2). By contrast, the MC3 receptor gene is found on a completely different chromosome 20(q13.2-q13.3). The chromosomal localization of the MC1 receptor gene is localized to 16q24.3.

The foregoing discussion discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims.

All publications cited herein are incorporated by reference.

    __________________________________________________________________________     SEQUENCE LISTING                                                               (1) GENERAL INFORMATION:                                                       (iii) NUMBER OF SEQUENCES: 23                                                  (2) INFORMATION FOR SEQ ID NO:1:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 951 base pairs                                                     (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: double                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: DNA (genomic)                                              (iii) HYPOTHETICAL: NO                                                         (iv) ANTI-SENSE: NO                                                            (vi) ORIGINAL SOURCE:                                                          (A) ORGANISM: Homo sapiens                                                     (ix) FEATURE:                                                                  (A) NAME/KEY: CDS                                                              (B) LOCATION: 1..951                                                           (ix) FEATURE:                                                                  (A) NAME/KEY: conflict                                                         (B) LOCATION: order(269..270, 488, 490..491)                                   (D) OTHER INFORMATION: /note="Differs from sequence                            published by Chhajlani and Wikberg in                                          five nucleotide and three amino acid                                           positions."                                                                    (ix) FEATURE:                                                                  (A) NAME/KEY: conflict                                                         (B) LOCATION: order(485, 488)                                                  (D) OTHER INFORMATION: /note="Differs from sequence                            published by Mountjoy, Robbins,                                                Mortrud and Cone in 2 nucleotide and 2                                         amino acid positions."                                                         (xi) SEQUENCE DESCRIPTION: SEQ ID NO:1:                                        ATGGCTGTGCAGGGATCCCAGAGAAGACTTCTGGGCTCCCTCAACTCC48                             MetAlaValGlnGlySerGlnArgArgLeuLeuGlySerLeuAsnSer                               151015                                                                         ACCCCCACAGCCATCCCCCAGCTGGGGCTGGCTGCCAACCAGACAGGA96                             ThrProThrAlaIleProGlnLeuGlyLeuAlaAlaAsnGlnThrGly                               202530                                                                         GCCCGGTGCCTGGAGGTGTCCATCTCTGACGGGCTCTTCCTCAGCCTG144                            AlaArgCysLeuGluValSerIleSerAspGlyLeuPheLeuSerLeu                               354045                                                                         GGGCTGGTGAGCTTGGTGGAGAACGCGCTGGTGGTGGCCACCATCGCC192                            GlyLeuValSerLeuValGluAsnAlaLeuValValAlaThrIleAla                               505560                                                                         AAGAACCGGAACCTGCACTCACCCATGTACTGCTTCATCTGCTGCCTG240                            LysAsnArgAsnLeuHisSerProMetTyrCysPheIleCysCysLeu                               65707580                                                                       GCCTTGTCGGACCTGCTGGTGAGCGGGACGAACGTGCTGGAGACGGCC288                            AlaLeuSerAspLeuLeuValSerGlyThrAsnValLeuGluThrAla                               859095                                                                         GTCATCCTCCTGCTGGAGGCCGGTGCACTGGTGGCCCGGGCTGCGGTG336                            ValIleLeuLeuLeuGluAlaGlyAlaLeuValAlaArgAlaAlaVal                               100105110                                                                      CTGCAGCAGCTGGACAATGTCATTGACGTGATCACCTGCAGCTCCATG384                            LeuGlnGlnLeuAspAsnValIleAspValIleThrCysSerSerMet                               115120125                                                                      CTGTCCAGCCTCTGCTTCCTGGGCGCCATCGCCGTGGACCGCTACATC432                            LeuSerSerLeuCysPheLeuGlyAlaIleAlaValAspArgTyrIle                               130135140                                                                      TCCATCTTCTACGCACTGCGCTACCACAGCATCGTGACCCTGCCGCGG480                            SerIlePheTyrAlaLeuArgTyrHisSerIleValThrLeuProArg                               145150155160                                                                   GCGCGGCAAGCCGTTGCGGCCATCTGGGTGGCCAGTGTCGTCTTCAGC528                            AlaArgGlnAlaValAlaAlaIleTrpValAlaSerValValPheSer                               165170175                                                                      ACGCTCTTCATCGCCTACTACGACCACGTGGCCGTCCTGCTGTGCCTC576                            ThrLeuPheIleAlaTyrTyrAspHisValAlaValLeuLeuCysLeu                               180185190                                                                      GTGGTCTTCTTCCTGGCTATGCTGGTGCTCATGGCCGTGCTGTACGTC624                            ValValPhePheLeuAlaMetLeuValLeuMetAlaValLeuTyrVal                               195200205                                                                      CACATGCTGGCCCGGGCCTGCCAGCACGCCCAGGGCATCGCCCGGCTC672                            HisMetLeuAlaArgAlaCysGlnHisAlaGlnGlyIleAlaArgLeu                               210215220                                                                      CACAAGAGGCAGCGCCCGGTCCACCAGGGCTTTGGCCTTAAAGGCGCT720                            HisLysArgGlnArgProValHisGlnGlyPheGlyLeuLysGlyAla                               225230235240                                                                   GTCACCCTCACCATCCTGCTGGGCATTTTCTTCCTCTGCTGGGGCCCC768                            ValThrLeuThrIleLeuLeuGlyIlePhePheLeuCysTrpGlyPro                               245250255                                                                      TTCTTCCTGCATCTCACACTCATCGTCCTCTGCCCCGAGCACCCCACG816                            PhePheLeuHisLeuThrLeuIleValLeuCysProGluHisProThr                               260265270                                                                      TGCGGCTGCATCTTCAAGAACTTCAACCTCTTTCTCGCCCTCATCATC864                            CysGlyCysIlePheLysAsnPheAsnLeuPheLeuAlaLeuIleIle                               275280285                                                                      TGCAATGCCATCATCGACCCCCTCATCTACGCCTTCCACAGCCAGGAG912                            CysAsnAlaIleIleAspProLeuIleTyrAlaPheHisSerGlnGlu                               290295300                                                                      CTCCGCAGGACGCTCAAGGAGGTGCTGACATGCTCCTGG951                                     LeuArgArgThrLeuLysGluValLeuThrCysSerTrp                                        305310315                                                                      (2) INFORMATION FOR SEQ ID NO:2:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 317 amino acids                                                    (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2:                                        MetAlaValGlnGlySerGlnArgArgLeuLeuGlySerLeuAsnSer                               151015                                                                         ThrProThrAlaIleProGlnLeuGlyLeuAlaAlaAsnGlnThrGly                               202530                                                                         AlaArgCysLeuGluValSerIleSerAspGlyLeuPheLeuSerLeu                               354045                                                                         GlyLeuValSerLeuValGluAsnAlaLeuValValAlaThrIleAla                               505560                                                                         LysAsnArgAsnLeuHisSerProMetTyrCysPheIleCysCysLeu                               65707580                                                                       AlaLeuSerAspLeuLeuValSerGlyThrAsnValLeuGluThrAla                               859095                                                                         ValIleLeuLeuLeuGluAlaGlyAlaLeuValAlaArgAlaAlaVal                               100105110                                                                      LeuGlnGlnLeuAspAsnValIleAspValIleThrCysSerSerMet                               115120125                                                                      LeuSerSerLeuCysPheLeuGlyAlaIleAlaValAspArgTyrIle                               130135140                                                                      SerIlePheTyrAlaLeuArgTyrHisSerIleValThrLeuProArg                               145150155160                                                                   AlaArgGlnAlaValAlaAlaIleTrpValAlaSerValValPheSer                               165170175                                                                      ThrLeuPheIleAlaTyrTyrAspHisValAlaValLeuLeuCysLeu                               180185190                                                                      ValValPhePheLeuAlaMetLeuValLeuMetAlaValLeuTyrVal                               195200205                                                                      HisMetLeuAlaArgAlaCysGlnHisAlaGlnGlyIleAlaArgLeu                               210215220                                                                      HisLysArgGlnArgProValHisGlnGlyPheGlyLeuLysGlyAla                               225230235240                                                                   ValThrLeuThrIleLeuLeuGlyIlePhePheLeuCysTrpGlyPro                               245250255                                                                      PhePheLeuHisLeuThrLeuIleValLeuCysProGluHisProThr                               260265270                                                                      CysGlyCysIlePheLysAsnPheAsnLeuPheLeuAlaLeuIleIle                               275280285                                                                      CysAsnAlaIleIleAspProLeuIleTyrAlaPheHisSerGlnGlu                               290295300                                                                      LeuArgArgThrLeuLysGluValLeuThrCysSerTrp                                        305310315                                                                      (2) INFORMATION FOR SEQ ID NO:3:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 1015 base pairs                                                    (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: double                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: DNA (genomic)                                              (iii) HYPOTHETICAL: NO                                                         (iv) ANTI-SENSE: NO                                                            (vi) ORIGINAL SOURCE:                                                          (A) ORGANISM: Homo sapiens                                                     (ix) FEATURE:                                                                  (A) NAME/KEY: CDS                                                              (B) LOCATION: 79..969                                                          (xi) SEQUENCE DESCRIPTION: SEQ ID NO:3:                                        AGGATCCTGAAGAATCAATCAAGTTTTCCGTGAAGTCAAGTCCAAGTAACATCCCCGCCT60                 TAACCACAAGCAGGAGAAATGAAGCACATTATCAACTCGTATGAAAACATC111                         MetLysHisIleIleAsnSerTyrGluAsnIle                                              1510                                                                           AACAACACAGCAAGAAATAATTCCGACTGTCCTCGTGTGGTTTTGCCG159                            AsnAsnThrAlaArgAsnAsnSerAspCysProArgValValLeuPro                               152025                                                                         GAGGAGATATTTTTCACAATTTCCATTGTTGGAGTTTTGGAGAATCTG207                            GluGluIlePhePheThrIleSerIleValGlyValLeuGluAsnLeu                               303540                                                                         ATCGTCCTGCTGGCTGTGTTCAAGAATAAGAATCTCCAGGCACCCATG255                            IleValLeuLeuAlaValPheLysAsnLysAsnLeuGlnAlaProMet                               455055                                                                         TACTTTTTCATCTGTAGCTTGGCCATATCTGATATGCTGGGCAGCCTA303                            TyrPhePheIleCysSerLeuAlaIleSerAspMetLeuGlySerLeu                               60657075                                                                       TATAAGATCTTGGAAAATATCCTGATCATATTGAGAAACATGGGCTAT351                            TyrLysIleLeuGluAsnIleLeuIleIleLeuArgAsnMetGlyTyr                               808590                                                                         CTCAAGCCACGTGGCAGTTTTGAAACCACAGCCGATGACATCATCGAC399                            LeuLysProArgGlySerPheGluThrThrAlaAspAspIleIleAsp                               95100105                                                                       TCCCTGTTTGTCCTCTCCCTGCTTGGCTCCATCTTCAGCCTGTCTGTG447                            SerLeuPheValLeuSerLeuLeuGlySerIlePheSerLeuSerVal                               110115120                                                                      ATTGCTGCGGACCGCTACATCACCATCTTCCACGCACTGCGGTACCAC495                            IleAlaAlaAspArgTyrIleThrIlePheHisAlaLeuArgTyrHis                               125130135                                                                      AGCATCGTGACCATGCGCCGCACTGTGGTGGTGCTTACGGTCATCTGG543                            SerIleValThrMetArgArgThrValValValLeuThrValIleTrp                               140145150155                                                                   ACGTTCTGCACGGGGACTGGCATCACCATGGTGATCTTCTCCCATCAT591                            ThrPheCysThrGlyThrGlyIleThrMetValIlePheSerHisHis                               160165170                                                                      GTGCCCACAGTGATCACCTTCACGTCGCTGTTCCCGCTGATGCTGGTC639                            ValProThrValIleThrPheThrSerLeuPheProLeuMetLeuVal                               175180185                                                                      TTCATCCTGTGCCTCTATGTGCACATGTTCCTGCTGGCTCGATCCCAC687                            PheIleLeuCysLeuTyrValHisMetPheLeuLeuAlaArgSerHis                               190195200                                                                      ACCAGGAAGATCTCCACCCTCCCCAGAGCCAACATGAAAGGGGCCATC735                            ThrArgLysIleSerThrLeuProArgAlaAsnMetLysGlyAlaIle                               205210215                                                                      ACACTGACCATCCTGCTCGGGGTCTTCATCTTCTGCTGGGCCCCCTTT783                            ThrLeuThrIleLeuLeuGlyValPheIlePheCysTrpAlaProPhe                               220225230235                                                                   GTGCTTCATGTCCTCTTGATGACATTCTGCCCAAGTAACCCCTACTGC831                            ValLeuHisValLeuLeuMetThrPheCysProSerAsnProTyrCys                               240245250                                                                      GCCTGCTACATGTCTCTCTTCCAGGTGAACGGCATGTTGATCATGTGC879                            AlaCysTyrMetSerLeuPheGlnValAsnGlyMetLeuIleMetCys                               255260265                                                                      AATGCCGTCATTGACCCCTTCATATATGCCTTCCGGAGCCCAGAGCTC927                            AsnAlaValIleAspProPheIleTyrAlaPheArgSerProGluLeu                               270275280                                                                      AGGGACGCATTCAAAAAGATGATCTTCTGCAGCAGGTACTGG969                                  ArgAspAlaPheLysLysMetIlePheCysSerArgTyrTrp                                     285290295                                                                      TAGAATGGCTGATCCCTGGTTTTAGAATCCATGGGAATAACGTTGC1015                             (2) INFORMATION FOR SEQ ID NO:4:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 297 amino acids                                                    (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:4:                                        MetLysHisIleIleAsnSerTyrGluAsnIleAsnAsnThrAlaArg                               151015                                                                         AsnAsnSerAspCysProArgValValLeuProGluGluIlePhePhe                               202530                                                                         ThrIleSerIleValGlyValLeuGluAsnLeuIleValLeuLeuAla                               354045                                                                         ValPheLysAsnLysAsnLeuGlnAlaProMetTyrPhePheIleCys                               505560                                                                         SerLeuAlaIleSerAspMetLeuGlySerLeuTyrLysIleLeuGlu                               65707580                                                                       AsnIleLeuIleIleLeuArgAsnMetGlyTyrLeuLysProArgGly                               859095                                                                         SerPheGluThrThrAlaAspAspIleIleAspSerLeuPheValLeu                               100105110                                                                      SerLeuLeuGlySerIlePheSerLeuSerValIleAlaAlaAspArg                               115120125                                                                      TyrIleThrIlePheHisAlaLeuArgTyrHisSerIleValThrMet                               130135140                                                                      ArgArgThrValValValLeuThrValIleTrpThrPheCysThrGly                               145150155160                                                                   ThrGlyIleThrMetValIlePheSerHisHisValProThrValIle                               165170175                                                                      ThrPheThrSerLeuPheProLeuMetLeuValPheIleLeuCysLeu                               180185190                                                                      TyrValHisMetPheLeuLeuAlaArgSerHisThrArgLysIleSer                               195200205                                                                      ThrLeuProArgAlaAsnMetLysGlyAlaIleThrLeuThrIleLeu                               210215220                                                                      LeuGlyValPheIlePheCysTrpAlaProPheValLeuHisValLeu                               225230235240                                                                   LeuMetThrPheCysProSerAsnProTyrCysAlaCysTyrMetSer                               245250255                                                                      LeuPheGlnValAsnGlyMetLeuIleMetCysAsnAlaValIleAsp                               260265270                                                                      ProPheIleTyrAlaPheArgSerProGluLeuArgAspAlaPheLys                               275280285                                                                      LysMetIlePheCysSerArgTyrTrp                                                    290295                                                                         (2) INFORMATION FOR SEQ ID NO:5:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 1080 base pairs                                                    (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: double                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: DNA (genomic)                                              (iii) HYPOTHETICAL: NO                                                         (iv) ANTI-SENSE: NO                                                            (vi) ORIGINAL SOURCE:                                                          (A) ORGANISM: Homo sapiens                                                     (ix) FEATURE:                                                                  (A) NAME/KEY: CDS                                                              (B) LOCATION: 1..1080                                                          (xi) SEQUENCE DESCRIPTION: SEQ ID NO:5:                                        ATGAGCATCCAAAAGAAGTATCTGGAGGGAGATTTTGTCTTTCCTGTG48                             MetSerIleGlnLysLysTyrLeuGluGlyAspPheValPheProVal                               151015                                                                         AGCAGCAGCAGCTTCCTACGGACCCTGCTGGAGCCCCAGCTCGGATCA96                             SerSerSerSerPheLeuArgThrLeuLeuGluProGlnLeuGlySer                               202530                                                                         GCCCTTCTGACAGCAATGAATGCTTCGTGCTGCCTGCCCTCTGTTCAG144                            AlaLeuLeuThrAlaMetAsnAlaSerCysCysLeuProSerValGln                               354045                                                                         CCAACACTGCCTAATGGCTCGGAGCACCTCCAAGCCCCTTTCTTCAGC192                            ProThrLeuProAsnGlySerGluHisLeuGlnAlaProPhePheSer                               505560                                                                         AACCAGAGCAGCAGCGCCTTCTGTGAGCAGGTCTTCATCAAGCCCGAG240                            AsnGlnSerSerSerAlaPheCysGluGlnValPheIleLysProGlu                               65707580                                                                       ATTTTCCTGTCTCTGGGCATCGTCAGTCTGCTGGAAAACATCCTGGTT288                            IlePheLeuSerLeuGlyIleValSerLeuLeuGluAsnIleLeuVal                               859095                                                                         ATCCTGGCCGTGGTCAGGAACGGCAACCTGCACTCCCCGATGTACTTC336                            IleLeuAlaValValArgAsnGlyAsnLeuHisSerProMetTyrPhe                               100105110                                                                      TTTCTCTGCAGCCTGGCGGTGGCCGACATGCTGGTAAGTGTGTCCAAT384                            PheLeuCysSerLeuAlaValAlaAspMetLeuValSerValSerAsn                               115120125                                                                      GCCCTGGAGACCATCATGATCGCCATCGTCCACAGCGACTACCTGACC432                            AlaLeuGluThrIleMetIleAlaIleValHisSerAspTyrLeuThr                               130135140                                                                      TTCGAGGACCAGTTTATCCAGCACATGGACAACATCTTCGACTCCATG480                            PheGluAspGlnPheIleGlnHisMetAspAsnIlePheAspSerMet                               145150155160                                                                   ATCTGCATCTCCCTGGTGGCCTCCATCTGCAACCTCCTGGCCATCGCC528                            IleCysIleSerLeuValAlaSerIleCysAsnLeuLeuAlaIleAla                               165170175                                                                      GTCGACAGGTACGTCACCATCTTTTACGCGCTCCGCTACCACAGCATC576                            ValAspArgTyrValThrIlePheTyrAlaLeuArgTyrHisSerIle                               180185190                                                                      ATGACCGTGAGGAAGGCCCTCACCTTGATCGTGGCCATCTGGGTCTGC624                            MetThrValArgLysAlaLeuThrLeuIleValAlaIleTrpValCys                               195200205                                                                      TGCGGCGTCTGTGGCGTGGTGTTCATCGTCTACTCGGAGAGCAAAATG672                            CysGlyValCysGlyValValPheIleValTyrSerGluSerLysMet                               210215220                                                                      GTCATTGTGTGCCTCATCACCATGTTCTTCGCCATGATGCTCCTCATG720                            ValIleValCysLeuIleThrMetPhePheAlaMetMetLeuLeuMet                               225230235240                                                                   GGCACCCTCTACGTGCACATGTTCCTCTTTGCGCGGCTGCACGTCAAG768                            GlyThrLeuTyrValHisMetPheLeuPheAlaArgLeuHisValLys                               245250255                                                                      CGCATAGCAGCACTGCCACCTGCCGACGGGGTGGCCCCACAGCAACAC816                            ArgIleAlaAlaLeuProProAlaAspGlyValAlaProGlnGlnHis                               260265270                                                                      TCATGCATGAAGGGGGCAGTCACCATCACCATTCTCCTGGGCGTGTTC864                            SerCysMetLysGlyAlaValThrIleThrIleLeuLeuGlyValPhe                               275280285                                                                      ATCTTCTGCTGGGCCCCCTTCTTCCTCCACCTGGTCCTCATCATCACC912                            IlePheCysTrpAlaProPhePheLeuHisLeuValLeuIleIleThr                               290295300                                                                      TGCCCCACCAACCCCTACTGCATCTGCTACACTGCCCACTTCAACACC960                            CysProThrAsnProTyrCysIleCysTyrThrAlaHisPheAsnThr                               305310315320                                                                   TACCTGGTCCTCATCATGTGCAACTCCGTCATCGACCCACTCATCTAC1008                           TyrLeuValLeuIleMetCysAsnSerValIleAspProLeuIleTyr                               325330335                                                                      GCTTTCCGGAGCCTGGAATTGCGCAACACCTTTAGGGAGATTCTCTGT1056                           AlaPheArgSerLeuGluLeuArgAsnThrPheArgGluIleLeuCys                               340345350                                                                      GGCTGCAACGGCATGAACTTGGGA1080                                                   GlyCysAsnGlyMetAsnLeuGly                                                       355360                                                                         (2) INFORMATION FOR SEQ ID NO:6:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 360 amino acids                                                    (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:6:                                        MetSerIleGlnLysLysTyrLeuGluGlyAspPheValPheProVal                               151015                                                                         SerSerSerSerPheLeuArgThrLeuLeuGluProGlnLeuGlySer                               202530                                                                         AlaLeuLeuThrAlaMetAsnAlaSerCysCysLeuProSerValGln                               354045                                                                         ProThrLeuProAsnGlySerGluHisLeuGlnAlaProPhePheSer                               505560                                                                         AsnGlnSerSerSerAlaPheCysGluGlnValPheIleLysProGlu                               65707580                                                                       IlePheLeuSerLeuGlyIleValSerLeuLeuGluAsnIleLeuVal                               859095                                                                         IleLeuAlaValValArgAsnGlyAsnLeuHisSerProMetTyrPhe                               100105110                                                                      PheLeuCysSerLeuAlaValAlaAspMetLeuValSerValSerAsn                               115120125                                                                      AlaLeuGluThrIleMetIleAlaIleValHisSerAspTyrLeuThr                               130135140                                                                      PheGluAspGlnPheIleGlnHisMetAspAsnIlePheAspSerMet                               145150155160                                                                   IleCysIleSerLeuValAlaSerIleCysAsnLeuLeuAlaIleAla                               165170175                                                                      ValAspArgTyrValThrIlePheTyrAlaLeuArgTyrHisSerIle                               180185190                                                                      MetThrValArgLysAlaLeuThrLeuIleValAlaIleTrpValCys                               195200205                                                                      CysGlyValCysGlyValValPheIleValTyrSerGluSerLysMet                               210215220                                                                      ValIleValCysLeuIleThrMetPhePheAlaMetMetLeuLeuMet                               225230235240                                                                   GlyThrLeuTyrValHisMetPheLeuPheAlaArgLeuHisValLys                               245250255                                                                      ArgIleAlaAlaLeuProProAlaAspGlyValAlaProGlnGlnHis                               260265270                                                                      SerCysMetLysGlyAlaValThrIleThrIleLeuLeuGlyValPhe                               275280285                                                                      IlePheCysTrpAlaProPhePheLeuHisLeuValLeuIleIleThr                               290295300                                                                      CysProThrAsnProTyrCysIleCysTyrThrAlaHisPheAsnThr                               305310315320                                                                   TyrLeuValLeuIleMetCysAsnSerValIleAspProLeuIleTyr                               325330335                                                                      AlaPheArgSerLeuGluLeuArgAsnThrPheArgGluIleLeuCys                               340345350                                                                      GlyCysAsnGlyMetAsnLeuGly                                                       355360                                                                         (2) INFORMATION FOR SEQ ID NO:7:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 996 base pairs                                                     (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: double                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: DNA (genomic)                                              (iii) HYPOTHETICAL: NO                                                         (iv) ANTI-SENSE: NO                                                            (vi) ORIGINAL SOURCE:                                                          (A) ORGANISM: homo sapiens                                                     (ix) FEATURE:                                                                  (A) NAME/KEY: CDS                                                              (B) LOCATION: 1..996                                                           (xi) SEQUENCE DESCRIPTION: SEQ ID NO:7:                                        ATGGTGAACTCCACCCACCGTGGGATGCACACTTCTCTGCACCTCTGG48                             MetValAsnSerThrHisArgGlyMetHisThrSerLeuHisLeuTrp                               151015                                                                         AACCGCAGCAGTTACAGACTGCACAGCAATGCCAGTGAGTCCCTTGGA96                             AsnArgSerSerTyrArgLeuHisSerAsnAlaSerGluSerLeuGly                               202530                                                                         AAAGGCTACTCTGATGGAGGGTGCTACGAGCAACTTTTTGTCTCTCCT144                            LysGlyTyrSerAspGlyGlyCysTyrGluGlnLeuPheValSerPro                               354045                                                                         GAGGTGTTTGTGACTCTGGGTGTCATCAGCTTGTTGGAGAATATCTTA192                            GluValPheValThrLeuGlyValIleSerLeuLeuGluAsnIleLeu                               505560                                                                         GTGATTGTGGCAATAGCCAAGAACAAGAATCTGCATTCACCCATGTAC240                            ValIleValAlaIleAlaLysAsnLysAsnLeuHisSerProMetTyr                               65707580                                                                       TTTTTCATCTGCAGCTTGGCTGTGGCTGATATGCTGGTGAGCGTTTCA288                            PhePheIleCysSerLeuAlaValAlaAspMetLeuValSerValSer                               859095                                                                         AATGGATCAGAAACCATTATCATCACCCTATTAAACAGTACAGATACG336                            AsnGlySerGluThrIleIleIleThrLeuLeuAsnSerThrAspThr                               100105110                                                                      GATGCACAGAGTTTCACAGTGAATATTGATAATGTCATTGACTCGGTG384                            AspAlaGlnSerPheThrValAsnIleAspAsnValIleAspSerVal                               115120125                                                                      ATCTGTAGCTCCTTGCTTGCATCCATTTGCAGCCTGCTTTCAATTGCA432                            IleCysSerSerLeuLeuAlaSerIleCysSerLeuLeuSerIleAla                               130135140                                                                      GTGGACAGGTACTTTACTATCTTCTATGCTCTCCAGTACCATAACATT480                            ValAspArgTyrPheThrIlePheTyrAlaLeuGlnTyrHisAsnIle                               145150155160                                                                   ATGACAGTTAAGCGGGTTGGGATCATCATAAGTTGTATCTGGGCAGCT528                            MetThrValLysArgValGlyIleIleIleSerCysIleTrpAlaAla                               165170175                                                                      TGCACGGTTTCAGGCATTTTGTTCATCATTTACTCAGATAGTAGTGCT576                            CysThrValSerGlyIleLeuPheIleIleTyrSerAspSerSerAla                               180185190                                                                      GTCATCATCTGCCTCATCACCATGTTCTTCACCATGCTGGCTCTCATG624                            ValIleIleCysLeuIleThrMetPhePheThrMetLeuAlaLeuMet                               195200205                                                                      GCTTCTCTCTATGTCCACATGTTCCTGATGGCCAGGCTTCACATTAAG672                            AlaSerLeuTyrValHisMetPheLeuMetAlaArgLeuHisIleLys                               210215220                                                                      AGGATTGCTGTCCTCCCCGGCACTGGTGCCATCCGCCAAGGTGCCAAT720                            ArgIleAlaValLeuProGlyThrGlyAlaIleArgGlnGlyAlaAsn                               225230235240                                                                   ATGAAGGGAGCGATTACCTTGACCATCCTGATTGGCGTCTTTGTTGTC768                            MetLysGlyAlaIleThrLeuThrIleLeuIleGlyValPheValVal                               245250255                                                                      TGCTGGGCCCCATTCTTCCTCCACTTAATATTCTACATCTCTTGTCCT816                            CysTrpAlaProPhePheLeuHisLeuIlePheTyrIleSerCysPro                               260265270                                                                      CAGAATCCATATTGTGTGTGCTTCATGTCTCACTTTAACTTGTATCTC864                            GlnAsnProTyrCysValCysPheMetSerHisPheAsnLeuTyrLeu                               275280285                                                                      ATACTGATCATGTGTAATTCAATCATCGATCCTCTGATTTATGCACTC912                            IleLeuIleMetCysAsnSerIleIleAspProLeuIleTyrAlaLeu                               290295300                                                                      CGGAGTCAAGAACTGAGGAAAACCTTCAAAGAGATCATCTGTTGCTAT960                            ArgSerGlnGluLeuArgLysThrPheLysGluIleIleCysCysTyr                               305310315320                                                                   CCCCTGGGAGGCCTTTGTGACTTGTCTAGCAGATAT996                                        ProLeuGlyGlyLeuCysAspLeuSerSerArgTyr                                           325330                                                                         (2) INFORMATION FOR SEQ ID NO:8:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 332 amino acids                                                    (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:8:                                        MetValAsnSerThrHisArgGlyMetHisThrSerLeuHisLeuTrp                               151015                                                                         AsnArgSerSerTyrArgLeuHisSerAsnAlaSerGluSerLeuGly                               202530                                                                         LysGlyTyrSerAspGlyGlyCysTyrGluGlnLeuPheValSerPro                               354045                                                                         GluValPheValThrLeuGlyValIleSerLeuLeuGluAsnIleLeu                               505560                                                                         ValIleValAlaIleAlaLysAsnLysAsnLeuHisSerProMetTyr                               65707580                                                                       PhePheIleCysSerLeuAlaValAlaAspMetLeuValSerValSer                               859095                                                                         AsnGlySerGluThrIleIleIleThrLeuLeuAsnSerThrAspThr                               100105110                                                                      AspAlaGlnSerPheThrValAsnIleAspAsnValIleAspSerVal                               115120125                                                                      IleCysSerSerLeuLeuAlaSerIleCysSerLeuLeuSerIleAla                               130135140                                                                      ValAspArgTyrPheThrIlePheTyrAlaLeuGlnTyrHisAsnIle                               145150155160                                                                   MetThrValLysArgValGlyIleIleIleSerCysIleTrpAlaAla                               165170175                                                                      CysThrValSerGlyIleLeuPheIleIleTyrSerAspSerSerAla                               180185190                                                                      ValIleIleCysLeuIleThrMetPhePheThrMetLeuAlaLeuMet                               195200205                                                                      AlaSerLeuTyrValHisMetPheLeuMetAlaArgLeuHisIleLys                               210215220                                                                      ArgIleAlaValLeuProGlyThrGlyAlaIleArgGlnGlyAlaAsn                               225230235240                                                                   MetLysGlyAlaIleThrLeuThrIleLeuIleGlyValPheValVal                               245250255                                                                      CysTrpAlaProPhePheLeuHisLeuIlePheTyrIleSerCysPro                               260265270                                                                      GlnAsnProTyrCysValCysPheMetSerHisPheAsnLeuTyrLeu                               275280285                                                                      IleLeuIleMetCysAsnSerIleIleAspProLeuIleTyrAlaLeu                               290295300                                                                      ArgSerGlnGluLeuArgLysThrPheLysGluIleIleCysCysTyr                               305310315320                                                                   ProLeuGlyGlyLeuCysAspLeuSerSerArgTyr                                           325330                                                                         (2) INFORMATION FOR SEQ ID NO:9:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 975 base pairs                                                     (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: double                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: DNA (genomic)                                              (iii) HYPOTHETICAL: NO                                                         (iv) ANTI-SENSE: NO                                                            (vi) ORIGINAL SOURCE:                                                          (A) ORGANISM: Mouse                                                            (ix) FEATURE:                                                                  (A) NAME/KEY: CDS                                                              (B) LOCATION: 1..975                                                           (xi) SEQUENCE DESCRIPTION: SEQ ID NO:9:                                        ATGAACTCCTCCTCCACCCTGACTGTATTGAATCTTACCCTGAACGCC48                             MetAsnSerSerSerThrLeuThrValLeuAsnLeuThrLeuAsnAla                               151015                                                                         TCAGAGGATGGCATTTTAGGATCAAATGTCAAGAACAAGTCTTTGGCC96                             SerGluAspGlyIleLeuGlySerAsnValLysAsnLysSerLeuAla                               202530                                                                         TGTGAAGAAATGGGCATTGCCGTGGAGGTGTTCCTGACCCTGGGTCTC144                            CysGluGluMetGlyIleAlaValGluValPheLeuThrLeuGlyLeu                               354045                                                                         GTCAGCCTCTTAGAGAACATCCTGGTCATTGGGGCCATAGTAAAGAAC192                            ValSerLeuLeuGluAsnIleLeuValIleGlyAlaIleValLysAsn                               505560                                                                         AAAAACCTGCACTCACCCATGTACTTCTATGTGGGCAGCTTAGCCGTG240                            LysAsnLeuHisSerProMetTyrPheTyrValGlySerLeuAlaVal                               65707580                                                                       GCCGACATGCTGGTGAGCATGTCCAATGCCTGGGAGACTGTCACCATA288                            AlaAspMetLeuValSerMetSerAsnAlaTrpGluThrValThrIle                               859095                                                                         TACTTGCTAAATAATAAACACCTGGTGATAGCCGACACCTTTGTGCGA336                            TyrLeuLeuAsnAsnLysHisLeuValIleAlaAspThrPheValArg                               100105110                                                                      CACATCGACAACGTGTTCGACTCCATGATCTGCATCTCTGTGGTGGCC384                            HisIleAspAsnValPheAspSerMetIleCysIleSerValValAla                               115120125                                                                      TCGATGTGCAGTTTGCTGGCCATTGCGGTGGACAGGTACATCACCATC432                            SerMetCysSerLeuLeuAlaIleAlaValAspArgTyrIleThrIle                               130135140                                                                      TTCTATGCCTTGCGCTACCACCACATCATGACCGCGAGGCGCTCGGGG480                            PheTyrAlaLeuArgTyrHisHisIleMetThrAlaArgArgSerGly                               145150155160                                                                   GTGATCATCGCCTGCATCTGGACCTTCTGCATAAGCTGCGGCATTGTT528                            ValIleIleAlaCysIleTrpThrPheCysIleSerCysGlyIleVal                               165170175                                                                      TTCATCATCTACTATGAGTCCAAGTATGTGATCATTTGCCTCATCTCC576                            PheIleIleTyrTyrGluSerLysTyrValIleIleCysLeuIleSer                               180185190                                                                      ATGTTCTTCACCATGCTGTTCTTCATGGTGTCTCTGTATATACACATG624                            MetPhePheThrMetLeuPhePheMetValSerLeuTyrIleHisMet                               195200205                                                                      TTCCTCCTGGCCCGGAACCATGTCAAGCGGATAGCAGCTTCCCCCAGA672                            PheLeuLeuAlaArgAsnHisValLysArgIleAlaAlaSerProArg                               210215220                                                                      TACAACTCCGTGAGGCAAAGGACCAGCATGAAGGGGGCTATTACCCTC720                            TyrAsnSerValArgGlnArgThrSerMetLysGlyAlaIleThrLeu                               225230235240                                                                   ACCATGCTACTGGGGATTTTCATTGTCTGCTGGTCTCCCTTCTTTCTT768                            ThrMetLeuLeuGlyIlePheIleValCysTrpSerProPhePheLeu                               245250255                                                                      CACCTTATCTTAATGATCTCCTGCCCTCAGAACGTCTACTGCTCTTGC816                            HisLeuIleLeuMetIleSerCysProGlnAsnValTyrCysSerCys                               260265270                                                                      TTTATGTCTTACTTCAACATGTACCTTATACTCATCATGTGCAACTCC864                            PheMetSerTyrPheAsnMetTyrLeuIleLeuIleMetCysAsnSer                               275280285                                                                      GTGATCGATCCTCTCATCTACGCCCTCCGCAGCCAAGAGATGCGGAGG912                            ValIleAspProLeuIleTyrAlaLeuArgSerGlnGluMetArgArg                               290295300                                                                      ACCTTTAAGGAGATCGTCTGTTGTCACGGATTCCGGCGACCTTGTAGG960                            ThrPheLysGluIleValCysCysHisGlyPheArgArgProCysArg                               305310315320                                                                   CTCCTTGGCGGGTAT975                                                             LeuLeuGlyGlyTyr                                                                325                                                                            (2) INFORMATION FOR SEQ ID NO:10:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 325 amino acids                                                    (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:10:                                       MetAsnSerSerSerThrLeuThrValLeuAsnLeuThrLeuAsnAla                               151015                                                                         SerGluAspGlyIleLeuGlySerAsnValLysAsnLysSerLeuAla                               202530                                                                         CysGluGluMetGlyIleAlaValGluValPheLeuThrLeuGlyLeu                               354045                                                                         ValSerLeuLeuGluAsnIleLeuValIleGlyAlaIleValLysAsn                               505560                                                                         LysAsnLeuHisSerProMetTyrPheTyrValGlySerLeuAlaVal                               65707580                                                                       AlaAspMetLeuValSerMetSerAsnAlaTrpGluThrValThrIle                               859095                                                                         TyrLeuLeuAsnAsnLysHisLeuValIleAlaAspThrPheValArg                               100105110                                                                      HisIleAspAsnValPheAspSerMetIleCysIleSerValValAla                               115120125                                                                      SerMetCysSerLeuLeuAlaIleAlaValAspArgTyrIleThrIle                               130135140                                                                      PheTyrAlaLeuArgTyrHisHisIleMetThrAlaArgArgSerGly                               145150155160                                                                   ValIleIleAlaCysIleTrpThrPheCysIleSerCysGlyIleVal                               165170175                                                                      PheIleIleTyrTyrGluSerLysTyrValIleIleCysLeuIleSer                               180185190                                                                      MetPhePheThrMetLeuPhePheMetValSerLeuTyrIleHisMet                               195200205                                                                      PheLeuLeuAlaArgAsnHisValLysArgIleAlaAlaSerProArg                               210215220                                                                      TyrAsnSerValArgGlnArgThrSerMetLysGlyAlaIleThrLeu                               225230235240                                                                   ThrMetLeuLeuGlyIlePheIleValCysTrpSerProPhePheLeu                               245250255                                                                      HisLeuIleLeuMetIleSerCysProGlnAsnValTyrCysSerCys                               260265270                                                                      PheMetSerTyrPheAsnMetTyrLeuIleLeuIleMetCysAsnSer                               275280285                                                                      ValIleAspProLeuIleTyrAlaLeuArgSerGlnGluMetArgArg                               290295300                                                                      ThrPheLysGluIleValCysCysHisGlyPheArgArgProCysArg                               305310315320                                                                   LeuLeuGlyGlyTyr                                                                325                                                                            (2) INFORMATION FOR SEQ ID NO:11:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 26 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: DNA (oligo)                                                (xi) SEQUENCE DESCRIPTION: SEQ ID NO:11:                                       TACGCAGCTGCCGCTACCACAGCATC26                                                   (2) INFORMATION FOR SEQ ID NO:12:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 30 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: DNA (oligo)                                                (xi) SEQUENCE DESCRIPTION: SEQ ID NO:12:                                       GAAGAGCAGTATGATGAAGGTGGGTCAGAT30                                               (2) INFORMATION FOR SEQ ID NO:13:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 14 amino acids                                                     (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:13:                                       AlaSerTyrSerMetGluHisPheArgTrpGlyLysProVal                                     1510                                                                           (2) INFORMATION FOR SEQ ID NO:14:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 22 amino acids                                                     (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:14:                                       AlaGluLysLysAspGluGlyProTyrArgMetGluHisPheArgTrp                               151015                                                                         GlySerProProLysAsp                                                             20                                                                             (2) INFORMATION FOR SEQ ID NO:15:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 12 amino acids                                                     (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:15:                                       TyrValMetGlyHisPheArgTrpAspArgPheGly                                           1510                                                                           (2) INFORMATION FOR SEQ ID NO:16:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 10 amino acids                                                     (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:16:                                       SerTyrSerMetGluHisPheArgTrpGly                                                 1510                                                                           (2) INFORMATION FOR SEQ ID NO:17:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 7 amino acids                                                      (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:17:                                       MetGluHisPheArgTrpGly                                                          15                                                                             (2) INFORMATION FOR SEQ ID NO:18:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 13 amino acids                                                     (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:18:                                       SerTyrSerMetGluHisPheArgTrpGlyLysProVal                                        1510                                                                           (2) INFORMATION FOR SEQ ID NO:19:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 10 amino acids                                                     (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:19:                                       MetGluHisPheArgTrpGlyLysProVal                                                 1510                                                                           (2) INFORMATION FOR SEQ ID NO:20:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 12 amino acids                                                     (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:20:                                       TyrValMetGlyHisPheArgTrpAspArgProGly                                           1510                                                                           (2) INFORMATION FOR SEQ ID NO:21:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 12 amino acids                                                     (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:21:                                       PheValMetGlyHisPheArgTrpAspArgPheGly                                           1510                                                                           (2) INFORMATION FOR SEQ ID NO:22:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 12 amino acids                                                     (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:22:                                       ThrValMetGlyHisPheArgTrpAspArgPheGly                                           1510                                                                           (2) INFORMATION FOR SEQ ID NO:23:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 12 amino acids                                                     (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:23:                                       TyrValMetGlyHisPheArgTrpAspArgProGly                                           1510                                                                           __________________________________________________________________________ 

What is claimed is:
 1. An isolated nucleic acid molecule encoding the amino acid sequence of Sequence Listing ID No.
 8. 2. A vector comprising the nucleic acid molecule of claim
 1. 3. A mammalian cell comprising the vector of claim
 2. 4. A bacterial cell comprising the vector of claim
 2. 5. A yeast cell comprising the vector of claim
 2. 6. An isolated nucleic acid molecule comprising a nucleotide sequence which hybrizes to the nucleic acid comprising the nucleotide sequence of Sequence Listing ID No. 7 in 6×SSC at 42° C. followed by washing with 1×SSC at 55° C., wherein said isolated nucleic acid molecule encodes a melanocortin-4 receptor.
 7. A vector comprising the nucleic acid molecule of claim
 6. 8. A mammalian cell comprising the vector of claim
 7. 9. A bacterial cell comprising the vector of claim
 8. 10. A yeast cell comprising the vector of claim
 9. 11. An isolated nucleic acid molecule comprising a nucleotide sequence which hybrizes to the nucleic acid comprising the complementary nucleotide sequence of Sequence Listing ID NO. 7 in 6×SSC at 42° C. followed by washing with 1×SSC at 55° C., wherein said isolated nucleic acid molecule encodes a melanocortin-4 receptor.
 12. A vector comprising the nucleic acid molecule of claim
 11. 13. A mammalian cell comprising the vector of claim
 12. 14. A bacterial cell comprising the vector of claim
 12. 15. A yeast cell comprising the vector of claim
 12. 16. A method for assaying the binding of a ligand to a melanocortin-4 receptor comprising the steps of:a) transfecting a cell which does not endogenously express melanocortin-4 receptor with a vector comprising a nucleotide sequence which hybridizes to the nucleic acid comprising the nucleotide sequence of Sequence Listing ID No. 7 in 6×SSC at 42° C. followed by washing with 1×SSC at 55° C., wherein said isolated nucleic acid molecule encodes a melanocortin-4 receptor, under conditions favorable for expression of melanocortin-4 receptor; b) contacting the cell with a ligand; and c) detecting ligand binding to the expressed melanoconin-4 receptor. 